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Classifying rockburst in deep underground mines using a robust hybrid computational model based on gene expression programming and particle swarm optimization

Quang-Hieu TRAN, Xuan-Nam BUI, Hoang NGUYEN

DOI: 10.11835/j.issn.2096-6717.2022.023

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In deep underground mining, rockburst is taken into account as an uncertainty risk with many adverse effects (i.e., human, equipment, tunnel/underground mine face, and extraction periods). Due to its uncertainty characteristics, accurate prediction and classification of rockburst tendency are challenging, and previous results are poor. Therefore, this study proposed a robust hybrid computational model based on gene expression programming (GEP) and particle swarm optimization (PSO), called GEP-PSO, to predict and classify rockburst tendency in deep openings with an accuracy improved. A different number of genes (from 1 to 4) and linking functions (e.g., addition, extraction, multiplication, and division) in the GEP model were also evaluated during the development of the GEP-PSO model aim. Geotechnical and constructive factors of 246 rockburst events were collected and used to develop the GEP-PSO models in terms of rockburst classification. Subsequently, a robust technique to handle missing values of the dataset was applied to improve the dataset""s attributes. The last step in the data processing stage is the feature selection to select potential input parameters using a correlation matrix. Finally, 13 hybrid GEP-PSO models were developed with different accuracies reported. The findings indicated that the GEP-PSO model with three genes in the structure of GEP and the multiplication linking function provided the highest accuracy (i.e., 80.49%). The obtained results of the best GEP-PSO model were then compared with a variety of previous models developed by previous researchers based on the same dataset. The comparison results also showed that the selected GEP-PSO model results outperform those of previous models. In other words, the accuracy of the proposed GEP-PSO model was improved significantly in terms of prediction and classification of rockburst grade. It can be considered widely applied in deep openings aiming to predict and evaluate the rockburst susceptibility accurately.
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Study on fatigue properties of welded details of steel bridge deck under temperature variation of pavement layer

WANG Da, SHAO Yu-xin, TAN Ben-kun, WANG Hong-hao

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In order to study the effect of temperature effect of asphalt pavement on the fatigue properties of welding details of orthotropic steel bridge deck, based on linear elastic fracture mechanics, this paper studied the effect of temperature effect of asphalt pavement on the stress of welding details and the stress intensity factor of fatigue crack tip at the weld toe of the roof, and established a crack correction coefficient prediction model based on XGBoost algorithm. The results show that the influence of asphalt pavement thickness and temperature effect on the fatigue properties of welded details of steel bridge deck cannot be ignored. Under high temperature conditions, the fatigue crack propagation rate at the weld toe of the roof is faster, and the crack shape ratio has a greater influence on the effective stress intensity factor. It is unsafe to evaluate the effect of pavement temperature effect on the fatigue performance of welded details of steel bridge deck only by stress. The stress at the weld toe of the roof and the effective stress intensity factor at the crack tip are nonlinearly related to the temperature effect of pavement layer. Combined with the prediction model of crack correction coefficient established in this paper, the effective stress intensity factor of fatigue crack tip can be effectively predicted, which is convenient for rapid evaluation of fatigue properties of welding details under the influence of temperature in engineering.
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Experimental and Constitutive Modeling of Bond-Slip Behavior at the Interface of Corroded H-shaped Steel and Concrete

Lin Yongjun, Yu Guofei, Zhong Shuiyun, Sun Liwen, Zhang Jing

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For unreinforced concrete structures utilizing H-shaped steel as a skeletal framework, concrete specimens integrated with H-shaped steel were prepared to represent varying degrees of corrosion, specifically rates of 0%, 5%, 10%, 15%, and 20%. Push-out tests were conducted to analyze the bond stress-slip relationship between H-shaped steel and concrete under different corrosion levels at the interface. An experimental method is proposed to derive the distribution of bond stress across the steel-concrete interface by measuring the compressive displacement on the surface of the concrete. Based on the observations from the tests, four microscopic mechanisms were proposed: chemical bonding, microscopic mechanical bonding, macroscopic mechanical bonding, and rust interface bonding, to explain the impact of corrosion on the bond performance of H-shaped steel in concrete. A constitutive relationship was constructed, incorporating the effect of the corrosion rate on bond stress slip, and an interface damage parameter was introduced to analyze the evolution of interface damage under varying corrosion rates. The research results indicated that the initial bond stiffness at the H-shaped steel-concrete interface increases with the corrosion rate. However, after reaching peak stress, the rate of decline in interface stiffness accelerates with increased corrosion. Notably, at higher corrosion rates (≥15%), the bond-slip curve displays a dual-peak feature, first ascending, then descending, followed by another rise, and ultimately declining. As the corrosion rate increases, the roles of chemical bonding and microscopic mechanical bonding become more dominant, while the contributions of macroscopic mechanical bonding and rust interface bonding diminish. The developed constitutive relationship, validated through comparative analysis with existing models, accurately describes the bond characteristics at the corroded H-shaped steel-concrete interface. Although an increase in corrosion rate hastens the reduction of interface stiffness, its influence on the extent of damage observed upon specimen failure is relatively limited.
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3D printed construction and mechanical properties analysis of prefabricated unreinforced concrete arch structure

HOU Renqian, LIN Wenyu, BAI Gang, WANG Li

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This paper conducts a feasibility study on 3D printed lightweight concrete arch structures from three aspects: design, construction, and load-bearing performance. Based on the characteristics of arch structure and 3D printing technology, a segment-assembly method was proposed to realize the accurate and fast assembly of arch structure. On this basis, five 3D printed lightweight arch structure specimens were constructed. The influence of three conditions, namely two-point concentration, three-point concentration, and uniformly distributed load, as well as the printing paths of "π", "W", and "M" cross-sections, was studied through experiments on the bearing performance of arch structures. Additionally, the mechanical behavior of 3D printed concrete arch structures with
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Study on crack propagation and energy evolution characteristics of water-saturated red sandstone containing hole

Zhang XIANG XIANG, Peng Chong, Liu Chengyu

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The uniaxial compression tests of dry and water-saturated red sandstone containing a single hole are conducted to analyze the characteristics of force and deformation, crack extension mechanism, acoustic emission characteristics and energy evolution based on the TAW-2000 test equipment, camera system and PCI–2 acoustic emission detection analysis system. The results show that the mechanical parameters of water-saturated rock sample are significantly lower than those of dry rock sample while the coefficients of brittle drop significantly increase. Crack propagation process can be divided into four stages: initial deformation stage, crack initiation stage and crack stable propagation stage and crack unstable propagation stage. The initial cracks and secondary cracks of water-saturated rock sample are more and longer, and significant force drop appears when initial cracks generate and cracks propagate unsteadily. The ring counts of rock samples focus on crack initiation and crack unstable propagation stage. In the water-saturated rock sample, the AE signals are less than dry rock sample. The AE signals during crack initiation stage are more than those during crack unstable propagation stage. Compared with the dry rock sample, the external energy is easier to dissipate in the water-saturated rock sample and the energy storage rate is slower to reach the peak. Therefore, the stored elastic energy is less in the water-saturated rock sample, which is more conducive to reducing the intensity of energy release during rock failure.
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Zero-valent copper catalysts derived from composite hydrogels efficiently activate persulfate for the degradation of chlorophenols

LIU Quan, LIU Zifan, YUE Cailiang, LIU Fuqiang

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Transition metal/carbon composite catalysts can effectively activate persulfate (PMS) to degrade organic pollutants. In this study, a simple pyrolysis method successfully transformed a composite hydrogeladsorbent that had adsorbed Cu(II) into a zerovalent copper/carbon composite catalyst (C-Cu), which efficiently activated PMS and rapidly degraded 2,4-dichlorophenol (2,4-DCP). Under conditions of pH 5, 5 mg of C-Cu dosage, and PMS concentration of 0.20 g·L-1, 2,4-DCP (0.1 mmol·L-1) was completely removed within 5 minutes, with a reaction kinetic constant as high as 3.434 2 min-1, an increase of 3 orders of magnitude over reported metal oxides. In compliance with the "Integrated Wastewater Discharge Standard "( GB8978-1996), the first-level standard, C-Cu can stably operate for 81.3 hours in a column dynamic reactor. Under the coexistence conditions of pH 5-9, conventional inorganic salts, and natural organic matter, the degradation of 2,4-DCP in the C-Cu/PMS system was not significantly inhibited, demonstrating good environmental tolerance. Moreover, the C-Cu/PMS system showed superior removal effects for various chlorophenol pollutants. Quenching experiments of active species and EPR test results consistently indicated that zerovalent copper serves as the activation site for PMS, generating a large amount of 1O2 and ·O2-. LC-MS analysis results suggested that 2,4-DCP undergoes processes such as dechlorination and ring-opening for degradation and mineralization. This research provides new insights for the resourceful utilization of hydrogel adsorbents and presents a novel approach for the development and application of cost-effective metal/carbon composite catalysts.
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Review of enhancing typical solid oxidants to degrade pollutants by reducing mediators

dong jiaojiao, liang zhijie, cui fuyi

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Chemical oxidation technology based on strong oxidants is an effective means to achieve the removal of recalcitrant organic pollutants. Compared with gas-form oxidants (e.g., ozone) and liquid-form oxidants (e.g., hydrogen peroxide), solid-form oxidants (e.g., permanganate) are relatively long-life, stable and impose much less safety risks, which were even more preferred for the degradation of organic pollutants in water. In recent years, in order to further improve the efficiency of solid oxidants in removing refractory pollutants, it has been widely recognized that the method of adding reducing mediators to enhance the removal of organic pollutants by oxidants has been widely recognized, especially in the degradation of emerging pollutants. This paper summarizes the latest progress of reducing mediator enhanced typical solid oxidants such as permanganate (KMnO4), ferrate (K2FeO4) and periodate (KIO4) degradation of organic pollutants. Moreover, the potential enhancement mechanisms of the reaction are emphatically expounded, and the research on chemical oxidation enhancement based on reducing mediators is prospected.
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Experimental study on anti-erosion performance of microbial combined fiber reinforced loess slope

Wang Baoquan, Xie Jiaheng, Guo Liang, Liu Fengwei, Wang Jia

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Rainfall erosion seriously threatens the stability of soil slopes and even induces instability and failure. In this study, jute fiber and microbial induced calcium carbonate precipitation (MICP) technology were combined to carry out ecological reinforcement of loess slope. Simulated rainfall test was used to analyze the improvement degree and influencing factors of slope erosion resistance. Scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS) were used to analyze the mechanism of mitigating rainfall erosion on loess slope from a micro perspective, and to explore the feasible means of mitigating rainfall erosion on loess slope. The results show that: (1) The addition of jute fiber can help to improve the rainfall erosion resistance of microbial mineralized loess, especially the medium and high content of medium and long size fiber. (2) The fiber reinforced loess treated by biomineralization can significantly resist the erosion of weak rainfall (6mm/h) and short-term erosion heavy rainfall (45mm/h). Under heavy rainfall conditions, the corrosion resistance increases with the increase of fiber content, but the increase range gradually decreased, and the highest corrosion resistance increased to 64.2%.(3) With the increase of fiber length and fiber content, the thickness difference between C2L5 and C8L25can reach 2.86 times.(4) There are two cementation modes in the surface layer of fiber-reinforced microbial mineralized loess: 1) the “intergranular filling” mode formed by the precipitation of calcium carbonate crystals in intergranular pores; 2) The “wrapped cementation” mode of calcium carbonate is formed by wrapping soil particles with fiber connection. The research results have practical guiding significance for the effective implementation of slope rainfall erosion prevention and control measures in the loess hilly and gully region.
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Efficiency and mechanism of ultraviolet/persulfate process for algal organic matter removal

Cui Fuyi, Yao Yingyun, Li Li, Zhao Zhiwei

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Algal blooms in drinking water sources produce a large amount of algal organic matter (AOM), and AOM can react with chlorine to produce disinfection by-products (DBPs), significantly endangering the water quality. Thus, the vacuum ultraviolet/persulfate (VUV/PS) process was employed to remove AOM and reduce the disinfection by-products (DBPs) formation. The VUV/PS process demonstrated superior efficiency in AOM removal compared to UV/PS, VUV, UV, and PS processes, achieving removal rates of dissolved organic carbon (DOC) and UV254 at 74.7 % and 70.7 %, respectively. Additionally, the removal rate of fluorescent organic matter surpasses 82.2 %. The PS dose and initial pH impacted AOM removal by influencing the transformation and concentration of reactive oxygen species (ROS). The primary ROS in VUV/PS process was hydroxyl radicals (HO?^{) and sulfate radicals (}SO4??^{), with steady-state concentrations of}4.78 × 10-13and 1.51 × 10-11^M-1^,respectively. AOM was effectively eliminated by VUV photolysis and ROS oxidation, with VUV enhancing the efficiency of AOM removal by facilitating the generation and conversion of ROS. Additionally, during subsequent chlorination, VUV/PS process significantly reduced the yield of DBPs and the theoretical toxicity. In conclusion, VUV/PS process exhibited significant potential for application in treating AOM-rich water.
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Gaussian Active Learning Algorithm for Extreme Event Estimation

Yang Haiting, Yin Weihao, Huang Yanwen, Yang Cheng, Hu Ruiqing

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Some major critical key structures will face extreme events during their service that may be overlooked disregarded due to their extremely low probability, but will result in serious losses if they occur. To accurately estimate the minimal failure probability of complex structures, this paper presents a method that can balance the accuracy and cost of calculating the probability of extreme events. By using an active learning strategy based on Gaussian surrogate metamodel, a search function is constructed that can effectively concentrate the training points on unilateral of the tail, and the function is better at finding the maximum error region weighted by the distribution function and re-investing the new training points. In order to verify the effectiveness of the algorithm, the nonlinear analysis of structural cracking is taken as an example. The relative error of the proposed algorithm is about 10% compared with MCS. The mean relative error of the estimated random variables is about 10%, indicating that this method can obtain acceptable statistical results. Compared with the results of AL-GP, the error expectation of the estimated random variables is reduced by 20%, indicating that the uncertainty at the tail can be reduced faster. The example proves that the algorithm is more sensitive to the tail and is suitable for the distribution calculation with potential tail risk.
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Study on the particle breakage and permeability characteristics of high dam rockfill under different vibratory compacting conditions

lirongjia, zhangjianqing, wangchenglong, wangfeng

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In high earth and rock dam engineering, the particle breakage and permeability characteristics of rockfill materials are important indicators that affect the physical and mechanical properties of dam materials. Indoor vibration tests were conducted on the scaled-down rockfill materials of Yulongkashi Hydropower Station to investigate the variations of parameters such as particle crushing and permeability coefficient of the rockfill materials under different vibration times.A three-dimensional structural model was established based on the particle size distribution curve, and seepage simulation was conducted on it. Changes in the pore structure and permeability characteristics of rockfill materials under different vibration and compacting durations were compared, and they were also compared with indoor experiments. Finally, some parameters affecting the permeability coefficient were subjected to fitting analysis, and the calculation formula for the permeability coefficient was obtained. The research results indicated that under the influence of vibration and compacting, the particle size distribution curve of the rockfill material became smoother, the particle arrangement became more compact, porosity, and permeability coefficient decreased, and water flow within the pore structure slowed down. The established three-dimensional structural model well reflected this process.
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Experimental study on the growthcharacteristics of dominant mold on the surface of farm house envelope in Lingnan

Jin Ling, Zhang Hongling, Liu Shengyu, Wang Jia, Zhang Hui, Edward Arens, Cong Peitong

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In order to reduce the safety and health hazards of the enclosure, on the basis of the field sampling and the orthogonal experiment, the influence of the growth characteristics of the dominant bacteria in order to expand the database of the dominant mold in the building and provide reasonable support for predicting the growth risk of mold under fluctuating temperature and humidity. First, mildew samples were obtained in Lingnan typical farm house by scraping, and high throughput sequencing was used to identify the dominant bacteria species; then 22 / 26 / 30℃ and 60% / 70% / 85% temperature and humidity combinations were used to study the growth characteristics of the dominant bacteria on Potato Dextrose Agar (PDA) and establish a kinetic model with time and temperature and humidity. Finally, 26 / 30 / 34℃ and 50% / 90% ambient temperature and humidity combinations in the artificial climate chamber to study the growth characteristics of the dominant bacteria on common building materials. The results show that in Lingnan area, the dominant fungus on the surface of the rural residential envelope structure with large white ash as the interior surface material are Cladosporium, Neoderiesia and Acremonium; 26℃ is the environmental temperature for the spore to grow and reproduce; the higher the relative humidity, the faster the growth; Gompertz model and response surface model can show the growth characteristics of spore on the culture medium.
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Influence of Leaching Substances from Tunnel Shotcrete on Water Quality

LUO Hesong, MENG Fanqiang, GONG Xun, LI Chuansong, DAI Jinsong, WANG Dongmei, GONG Zhengjun

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Tunnel construction drainage and sewage diversion is an important engineering technology to reduce tunnel construction sewage discharge. However, the leaching substances of unstable tunnel shotcrete can affect the drainage water quality. Therefore, the study of the influence of leaching substances on water quality during the stabilization process of shotcrete is of great significance for the precise implementation of sewage separation technology. The concrete test blocks are prepared using shotcrete materials from tunnel construction. Firstly, the leaching components were analyzed through static experiments. Then, the effects of curing times, the ratio of water to concrete (L/S ratio), and the contact areas on the pH and alkalinity of the leaching solution were explored through 14 days dynamic leaching experiments continuously. The leaching process and mechanism were also explored combined with characterization analysis. The static experimental results indicate that the large release of alkaline substances in shotcrete leads to a rapid increase in the pH value of water, which is the main reason affecting water quality. The dynamic experimental results show that when the curing time of the concrete is less than three days, the calcium hydroxide crystal inside the concrete is not solidified by the C-S-H gel, which is easy to continue to precipitate, leading to the pH value of the contact water sample exceeding the standard. With the increase of curing time, the leaching alkaline substances decrease significantly. When the maintenance time reaches 28 days, the pH value of the leaching solution drops below 9, which can meet the requirements of comprehensive sewage discharge. When the L/S ratio is low, the leaching substance has a significant impact on the pH and alkalinity of the water sample. When the L/S ratio exceeds 40:1, the leaching substance has no significant impact on the water quality of the water sample. The larger the contact area between concrete and water samples, the easier it is for alkaline substances in concrete to dissolve and precipitate, and the more significant the impact on the pH and alkalinity of water quality. This study provides important theoretical basis for the on-site construction design of drainage and sewage diversion technology in tunnel construction.
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Distribution and suitability of city trees in China under climate change

GU Jingxian, YANG Yongchuan, MOU Wenbo, JIN Cheng

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City trees are an important part of urban landscaping and greening. In recent years, climate change has caused the migration of city trees, which affects the sustainable development of urban living environment. Therefore, it is urgent to understand the suitable distribution areas and habitats of city trees under climate change. Based on the distribution status of 50 species of city trees in 147 cities in China, we used the MaxEnt model to study the changes of suitable distribution zones of city trees under the climate of 2070s, and analyzed the future suitability of city trees through the overlap of distribution zones and urban administrative areas, so as to provide a basis for urban landscape planning in China. The results showed that: (1) there are 50 common city trees in China, belonging to 24 families and 42 genera, among which Styphnolobium japonicum, Cinnamomum camphora and Ginkgo biloba are the most widely used, 65.6% of cities use native species, and 89.5% of cities use broadleaf trees. (2) Under climate change, the direction of movement of suitable areas for city trees is complex, and the area tends to contract (68%), with Rhizophora. apiculata and Ulmus. laevis showing the greatest changes. (3) The future suitability of city trees is related to the source and urban location, and the suitability of native plants is higher to exotic species; the proportion of high suitability municipal trees is higher in northern cities, while low suitability city trees dominate in the south. In the future, comprehensive considerations should be made to guide the high-quality development of urban landscaping according to local conditions.
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Review of Mn-based materials for phosphate removal

ZHAI Jun, He Wen-tao, Liu Wen-bo

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Eutrophication is a global issue that threatens drinking water safety and even the entire ecological balance. The excessive discharge of phosphorus (mainly in phosphate) in water is one of the important reasons for eutrophication. Therefore, controlling the concentration of phosphorus in water, especially phosphate concentration, is of great significance. Mn-based materials have good potential for phosphate removal, but existing reviews lack a systematic summary of them, making them a metal-based materials that have not received much attention. ln fact, research on Mn-based materials in the field of phosphate removal has evolved from single manganese oxides to mixed metal oxides and hydroxides, metal-support composite materials, and layered double hydroxides (LDHs). Meanwhile, the emergence of emerging methods such as electro assisted adsorption and plasma further enhances the ability of Mn-based materials to remove phosphates. The present article reviews the effects and mechanisms of phosphate removal using different Mn-based materials, and evaluates the application prospects of phosphate removal using different Mn-based materials. Then, from the perspective of increasing pHpzc or enhancing electrostatic effects, several methods for enhancing phosphate removal in Mn-based materials are analyzed and summarized. Finally, based on existing research, the current shortcomings and future development directions are proposed in order to provide reference for future research on phosphate removal using Mn-based materials.
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Machine learning-based investigation of uplift resistance in special-shaped shield tunnels using numerical finite element modelling

Zhang Wengang, Ye Wenyu, Sun Weixin, Liu Zhicheng, Li Zhengchuan, Yu Yongtang

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The uplift resistance of the soil overlying shield tunnels significantly impacts their anti-floating stability. However, the research on uplift resistance concerning special-shaped shield tunnels is limited. This study utilizes numerical simulation and machine learning techniques to explore this research field. It presents a summary of special-shaped tunnel geometries and introduces a shape coefficient. Through Plaxis3D finite element software, the study simulates six key parameters—shape coefficient, burial depth ratio, tunnel"s longest horizontal length, internal friction angle, cohesion, and soil submerged bulk density—that impact uplift resistance across different conditions. Employing XGBoost and ANN machine learning methods, the feature importance of each parameter was analyzed based on the numerical simulation results. The findings demonstrate that a tunnel shape more closely resembling a circle leads to reduced uplift resistance in the overlying soil, whereas other parameters exhibit contrary effects. Furthermore, the study reveals a diminishing trend in the feature importance of buried depth ratio, internal friction angle, tunnel longest horizontal length, cohesion, soil submerged bulk density, and shape coefficient in influencing uplift resistance.
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Energy flexibility potential of short-term HVAC system management in office buildings under the typical and extreme weather conditions in China in cooling season

Huang Bingjie, Liu Meng, Li Ziqiao

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To face the challenge of mismatching between power supply and demand, building flexibility is required to schedule flexible loads and improve the coordination of power grids. Due to climate change, mounting evidence of extreme weather and climate event has been reported. Understanding the effectiveness of flexibility management strategies under different climate conditions is essential. Using the typical and extreme weather data of cities in five major climate zones of China, this study investigates the energy flexibility potential of an office building under three short-term HVAC management strategies, aiming to discover its effectiveness under different local outdoor climates in China’s context. The results show that the peak load flexibility and overall energy performance of the three short-term strategies were impacted by outdoor climate conditions. The peak load reduction rate of pre-cooling and zone temperature reset strategies declined linearly as the increase of outdoor temperature. In the extreme climate condition, the daily peak-load time was found to be over two hours earlier than that of the typical condition, and the intensive solar radiation in the extreme condition could result in a weak correlation between peak load reduction and outdoor temperature and risk of maintaining the comfortable indoor thermal environment.
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Damage identification method of beam string structures with improved configuration based on modal parameters

renyichun, chenjing, jiangyoubao, zhouhao

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In order to clarify the damage identification method applicable to each member type of beam string structures with improved configuration of lower chord and strut, and to reduce the misjudgment at non-damaged members, in this paper, a damage identification index of sub-component curvature variation based on structural mode is proposed, the validity of the index is illustrated by analyzing a simply supported beam structure with a simple structural form. The finite element software ANSYS was used to establish the analysis model of beam string structures with improved configuration of lower chord and strut, the damage of the member is simulated by reducing the elastic modulus of the member element. Considering the symmetry and complexity of the structure, damage conditions of single damage, multiple damage, and small damage level were set up in the mid-span, quarter-span, and near-bearing end bars, respectively, the improved curvature absolute difference index of sub-component and the sub-component curvature variation based on structural mode proposed in this paper are used for the comparative analysis of damage identification. The results show that the index of sub-component curvature variation based on structural mode can achieve the precise localization of single-damaged and multiple-damaged structures, and this index is also very sensitive to working conditions with a small degree of damage, which can be used as an effective method for the damage identification of the beam string structures with improved configuration of lower chord and strut.
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Research progress and prospect of effects of productive dust particles on individual health

Liuyalin, chaiyihua, huangyanqiu

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In recent years, the burden of health risks caused by dust particles generated by industrial operations has gradually increased. A large number of studies have shown that long-term exposure to productive dust particles is closely related to workers' respiratory occupational diseases, and the relationship between indoor exposure to dust particles in industrial buildings and adverse health effects of workers has been clarified. It is of great significance for scientific evaluation of industrial building environmental safety and guarantee of workers' health. At present, the research on toxicity and biological effects of dust particles has gradually shifted the focus of research on dust particle exposure from environmental assessment to individual health effects. However, the correlation between exposure to industrial dust particles and health effects has not yet been fully clarified, and the impact of exposure to different types and levels of dust particles on health effects in industrial sites remains to be clarified. This paper reviews the progress of research on the health effects of industrial dust particles at home and abroad from three aspects: the possible damage caused by dust particles on respiratory system health, the correlation of health effects of dust exposure and health risk assessment, and clarifies the effects of exposure on health and the current theoretical deficiencies in quantifying the mechanism of action of dust particles based on exposure effect models. And the urgency of effective biomarker selection, to provide reference information for the future scientific protection of workers' health, different types of industrial environmental monitoring guidelines and development of control and improvement means.
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Effects of bender element arrangement and grouting method on small strain shear modulus of MICP-cemented sand

ZHANG Lei, LI Haoyu, HU Jian, Tao Xu, SHI Jinquan

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In geotechnical engineering, the small-strain shear modulus of sand Gmax is an important mechanical parameter. The isotropic consolidation tests were carried out on artificial glass sand, combined with multi-direction bender element tests. The effects of MICP reinforcement methods and bender element arrangement on Gmax of glass sand were investigated. The test results show that the development rules of shear wave velocity VS, small strain stiffness Gmax and stiffness anisotropy GHH/GHV of glass sands reinforced by different methods are different. After MICP reinforcement, the Gmax of glass sand is increased. Among them, "low pH one-phase method + direct back pressure after injection of reaction solution" has the largest Gmax increase, and the small-strain stiffness ratio (Gload max /Gunload max) has the largest decrease. Due to the nonuniformity reinforcement, the placement height of bender element on the side wall also has a certain influence. Based on the test results in this study, it is recommended to arrange the HH and HV bender elements at the same plane to further discuss the effect of MICP on small strain stiffness anisotropy. Otherwise, the test error caused by reinforcement inhomogeneity can not be avoided.
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Multi-objective Optimization Modeling and Solution Methods for Deformation Control Design of Pit Support Structures

Ding Xiaowen, Long Sihua, Ye Kuai, WAN Qiwei, Ding Haibin, Xu Changjie

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In response to the increasing design requirements for foundation pit engineering in urban construction, this study proposes a multi-objective optimization model that integrates deformation control with economic principles for improving the design of foundation pit support structures. The model comprises three main parts: a bilateral coupling deformation calculation model for foundation pit support, a multi-objective optimization model that simultaneously considers deformation control and economic efficiency, and a meta-heuristic optimization algorithm for model search and solution. By analyzing and comparing the efficacy of four meta-heuristic algorithms and conducting detailed analysis with practical engineering cases, the study demonstrates that the proposed method can effectively achieve deformation control design for foundation pit support structures, with accuracy heavily reliant on the deformation calculation model and economic model. This research offers a new approach for the design of deformation control in foundation pit engineering, providing practical application value.
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Parameter Analysis Study of a Long-Span Floating Suspension Bridge’s Tension Leg Platform under Vehicle Loading

BAI Zhiyu, WEI Kai, ZHANG Feng, ZHANG Zeduan

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Construction schemes for long-span floating suspension bridges based on tension leg platforms have high application prospects in high water depth and soft soil environments. Due to their weak foundation stiffness, vehicle loads may induce significant vibrations in bridges. This phenomenon can be mitigated by adjusting the parameters of the tension leg platform. However, there is limited research on this novel long-span floating bridge under vehicle loads. However, the feasibility and applicability of such schemes need validation. This paper utilized finite element software to compute the response of a floating suspension bridge model under the vehicle load. The effect of changes in the submerged depth and cable inclination angle on the response were investigated using methods such as modal analysis. The study revealed that adjusting the parameters of the submerged depth and cable inclination angle primarily alters the first two vibrational modes, significantly affecting lateral responses. Increasing the submerged depth of the platform and adding inclined tension leg cables effectively reduce the vibrations under the vehicle load. Additionally, the optimal modification of the cable inclination angle requires specific analysis. Therefore, during the design phase, relevant tension leg platform design parameters are crucial for finding the most suitable configuration, which can enhance the overall feasibility and applicability of floating bridges under the vehicle load.
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Numerical study on deformation of pit tilted strut of concrete-filled steel tube with belled bearing base

ZHANG Wengang, YAN Yumiao, YUAN Yuntao, CHEN Chunxia, MOU Yunzhen, LI Yongqin

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With the surge in the "double-carbon" mandate within geotechnical engineering, there's a notable rise in eco-conscious underground construction technologies. Among these, the bottom-expanding load-bearing steel pipe concrete inclined support stands out as a novel foundation pit excavation support system. Multiple engineering cases affirm the efficacy of this inclined support system, yet its operational mechanism warrants deeper exploration. Employing finite element numerical simulation, this study delves into the deformation traits of such bottom-spreading inclined braces within real pit excavation projects. It scrutinizes the impact of soil stiffness and the inclined brace's angle on support efficacy. Results indicate that the extended bottom inclined brace significantly controls soil deformation during foundation pit excavation, particularly in softer soil regions. An increased inclined angle enhances lateral force support, augmenting bearing capacity. This proves instrumental in restraining soil and retaining wall deformation. However, it comes at a heightened project cost, demanding careful selection contingent on specific engineering conditions.
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Numerical simulation of rainfall-induced deformations of reinforced embankments considering the hydro-mechanical coupled behavior of unsaturated soils

WU Hao, LUAN Xiaohan, ZENG Changxian, ZHENG Junjie, ZHENG Yewei

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A constitutive model that considers the hydro-mechanical coupled behavior of unsaturated soils was introduced and implemented in the finite difference program FLAC. Triaxial test data involving loading and wetting paths were used to validate the constitutive model implemented in FLAC. Using the validated constitutive model to simulate the embankment fill, the deformation behavior of unsaturated reinforced embankments subjected to rainfall infiltration was investigated. The influence of geosynthetic reinforcement on the wetting-induced deformations of embankments was investigated. The results show that the reinforcements have negligible impact in the unreinforced zone. However, the reinforcements can effectively reduce the volumetric strains and shear strains of the soil elements in the reinforced zone. The reinforcements have a negligible effect on surface settlement in the unreinforced zone near the centerline of embankment but are effective in reducing surface settlement at the shoulder and lateral displacements of embankment slope under rainfall. The longer reinforcements are more efficient in reducing surface settlements of embankment and lateral displacements of slope and could also increase the distance between the slope surface and the potential failure surface.
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Study on seismic response law of ECC pile-energy dissipation anchor ductile retaining structure

DING Xuanming, LIU Xuecheng, Wang Chunyan, Ren Jiyu, Liu Shimin

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Pile-anchor structure is one of the most common supporting structures in earthquake and landslide control. How to improve its seismic toughness under strong earthquakes is a problem worth studying. In this study, a viscous damper is set on the anchor cable, and ECC materials are used to make anti-slide piles to construct a new type of pile-anchor structure system, which optimizes the seismic performance of the pile-anchor structure. Through shaking table test, the dynamic response laws of the new pile-anchor structure are obtained from the aspects of macroscopic failure phenomenon, model dynamic characteristics, acceleration response, pile displacement response, dynamic bending moment response, dynamic axial force response, etc., so as to reveal the seismic performance and action mechanism of the new pile-anchor structure. The test results show that the installation of the damper can reduce the dynamic axial force of the anchor cable and the seismic energy transferred to the pile, and the use of ECC material can effectively improve the toughness of the pile and enhance the energy dissipation capacity of the anti-slide pile under earthquake action. The combined use of the two can significantly improve the seismic performance of the supporting structure. The research results can provide reference for the seismic performance optimization and design of pile-anchor structure.
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Effect of moisture content on the shear properties of granite residual soil-geotextile interface

Liu Feiyu, Song Wenjie, Fu Dongping

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As a special soil widely distributed in the southeast coastal areas of China, granite residual soil is greatly influenced by water, leading to significant changes in its mechanical properties and an increased susceptibility to disasters. To investigate the shear characteristics of the granite residual soil-geotextile interface, the effects of different moisture content (12%, 16%, 20%, 24%) and vertical stresses (50 kPa, 100 kPa, 150 kPa, 200 kPa) were analyzed through large-scale direct shear tests conducted indoors. Based on the findings of indoor experiment, the PFC2D model was established, to reveal the meso-mechanism? behavior of the granite-residual soil-geotextile interface under varying moisture content conditions during the shear process. The results revealed that the interfacial shear strength and friction angle decreases with the increasing moisture content, while the similar cohesion increases first and then decreases, reaching the maximum value at 16% moisture content. Numerical simulation demonstrated that the shear zones are distributed in strips above the fabric, and the thickness of the shear bands increases in a predictable manner with the displacement field of the particles in the upper section.? The presence of the fabric prevents the penetration of force chains between the upper and lower sections, and the primary directions of normal and tangential contact forces remain consistent under different moisture content conditions. Energy dissipation mainly occurs through slip, with the loss of energy between the soil and fabric significantly lower than that between soil particles.
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The stability study of heavy metal ions mineralized by non-CaCl2 soybean urease

Wu Zhengyu, Duan Chaolong, Xu Xiangchun, Zhang Jianwei, Bian Hanliang, Yang Qingbo

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In order to explore the effect of soybean urease-free CaCl2 curing treatment on the long-term stability of lead and zinc contaminated soil without greatly improving the strength of cultivated soil. The long-term stability of contaminated soil under complex environment such as dry-wet cycle, freeze-thaw cycle and acid rain leaching was studied by pH value, leaching rate of heavy metal ions and occurrence forms of heavy metals in soil. The results showed that the surface strength of lead and zinc contaminated soil treated with soybean urease-free CaCl2 was significantly lower than that of adding calcium source, and the permeability coefficient increased. Under the influence of long-term environmental conditions, the pH value of soil decreased slowly and was still weakly alkaline, and the leaching rate of heavy metals increased gradually. Under the action of acid rain, with the increase of pH of acid rain solution, the content of Pb2+ and Zn2+ in the leachate decreased gradually, and all met the requirements of the code for the disposal of hazardous wastes. In addition, the effects of different types of acid rain on the repaired soil are also different, and the stability of the repaired soil under the action of sulfuric acid rain is better than that of nitric acid rain.
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Experimental study on feasibility and parameter optimization of ultrasonic dredging technology in combined drainage systems

TANG Zhenzhen, MENG Daizong, XU Haolian, ZHU Ruilin, LI Huaizheng

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The presence of large quantities of sediments in urban drainage systems can lead to pipeline blockage and overflow contamination in rainy day. Ultrasound, as a clean physical treatment method, may destabilize sediment aggregates, thus removing sediment during the dry season to maintain sewer function. To investigate the feasibility and optimal treatment conditions of ultrasonic technology for actual dredging, orthogonal experiments were designed to explore the effectiveness of ultrasonic dredging and the impact of five key factors on ultrasonic dredging. The results showed that ultrasonic treatment exhibited good effects on improving pipe siltation, with the shear resistance of the sediments (EPS) reduced to 26.4-91.5% of the control group after ultrasonic action, and a large number of EPS associated with adhesion were decomposed in the pipe sediments. Correlation analysis showed that the damage of EPS was an important reason for the decrease in the scour resistance of the sediments. The order of the impact of five key factors on ultrasonic dredging is: ultrasonic power> probe distance from mud surface> action time> sediment thickness> ultrasonic frequency. The optimal working conditions of ultrasonic dredging are: power 220w, frequency 50Khz, processing time 200s, distance from the sediment surface of 3cm. Explored the variation of dredging effect with sediment thickness, and found that ultrasonic dredging has a good effect on sediment with a thickness of ≤7cm, and obviously decayed beyond this range. Based on this, further exploration was conducted on the changes in the properties of sediment along the depth direction after ultrasonic action.
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Activation of oxygen by manganese sulfide to produce reactive oxygen: species, kinetics and reaction mechanisms

Li jianing, Yuan yibo, Zhang junda, Li ning, Guo qin, Yu yangyi, Huang qianqian, Wei xipeng, Jiang jin

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Iron/manganese sulfides widely exist in the anoxic underground environment. The element cycling process of Fe, Mn and S controls the material cycling and energy conversion process in the underground environment. Usually, iron sulfides can produce reactive oxygen species (ROS) with O2 disturbance by providing electrons to reduce O2. However, the specific mechanism of ROS production by the reaction between manganese sulfides and O2 is still unclear. Herein, manganese sulfide (MnS), a prevalent natural form of manganese sulfide minerals, was studied to explore the species, kinetics and reaction mechanisms of ROS generated through the activation of O2 by MnS. The results showed that MnS could activate O2 to produce a large number of ROS, including ?OH, H2O2 and O2?-. The maximum cumulative ?OH reached 389.0 μM using 1 g/L MnS with initial pH 3 at 200 r/min stirring speed, and the yield of ?OH was 4.4 and 149.6 times greater than that of FeS and FeS2 oxygenation under the same molar concentration, respectively. The reduction of O2 by MnS resulted in the generation of O2?- through the transfer of single electron, followed by the acquisition of an additional electron to form H2O2. The dissolved Mn2+ catalyzed O2/H2O2 to produce ?OH with low efficiency, but the structural Mn(II) could efficiently catalyze H2O2 to produce abundant ?OH, indicating that heterogeneous catalysis of H2O2 played an important role in ?OH production. Additionally, the soluble S2- might facilitate electrons transfer to high-valence Mn(III)/Mn(IV) to promote the regeneration of structural Mn (II), which further promoted the production efficiency of ?OH via strengthening the electron cycle of Mn(II) /Mn(III). Furthermore, the degradation efficiency of phenol (5 mg/L) by MnS/O2 system was up to 97.4% within 3 h, indicating that the activation of O2 by MnS showed great potential in the environmental remediation.
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Research advances in coagulants prepared through the resourceful utilization of aluminum dross

ZHENG huaili, ZHANG weizhen, LIU shuang, SUN qiang, JIANG xincheng, DING wei

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In order to fulfill the "dual-carbon" goals, the effective utilization of secondary resources and the prevention of environmental pollution are among the tasks essential for sustainable development. Aluminum dross, as a secondary resource, can be beneficially repurposed into coagulants for water treatment through appropriate resource utilization, facilitating resource conservation, cost reduction, and addressing the issue of harmless aluminum dross disposal. It could also help with the problem of how to safely handle aluminum dross by using good resource preparation methods for coagulants. The paper systematically reviews the important raw materials for aluminum-based coagulants and five types of aluminum dross-based coagulants, including calcium aluminate, aluminum sulfate, polyaluminum sulfate, polyaluminum sulfate chloride, polyaluminum ferric sulfate, and polyaluminum chloride. It elaborates on their characteristics, preparation methods, research progress, and conducts an economic analysis of the production of aluminum dross-based coagulants. Currently, the large-scale application of aluminum dross-based coagulants still faces certain challenges. However, continued focus and beneficial developments in the future are expected to bring about more significant economic and environmental benefits, contributing significantly to the high-quality, green, and sustainable development of the water treatment and aluminum industries.
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Experimental study on seismic performance of the novel concrete-filled square steel tubular spliced columns with grouting anchor connections

zhengliwen, lizhi, zhaoliang, hushaowei, lijinghao, qihao

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A novel design method for concrete-filled square steel tubular spliced columns with grouting anchor connections is proposed in this paper to increase the assembly efficiency, improve the seismic performance and reduce production costs of the column members in the steel-concrete composite structures. The seismic performances of novel spliced columns with different reinforcement ratios, reinforcement configurations and column-column joint positions were tested via quasi-static loading test on 5 spliced columns and one monolithic casting column with scale ratio of 2. The results showed that the failure modes and process of the novel spliced column members under low cyclic loading are similar to those of the reference member. The hysteretic curves of the novel spliced columns are full, and the energy dissipation capacity, load bearing capacity degradation and stiffness were advantageous than those of the reference column member. In particular, the P-type members with the column-column joint located in the column inflection point area had a better ductility and deformation capacity under the seismic effect. The test results identify that the novel spliced columns designed method proposed is scientific and has application potential to improve the overall seismic performance of the steel-concrete composite frame structures.
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Research on deformation characteristics of energy pile group under horizontal load

WU Qi, DING Xuanming, WANG Chenglong, ZHANG Dingxin

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Nowadays, the research on the thermodynamic characteristics of the energy pile group foundation under external load mainly focuses on the vertical load, but the study on the impact of horizontal load is limited. To investigate the deformation characteristics of horizontally loaded energy pile groups under asymmetric heating or cooling conditions, a single pile within the 2×2 energy pile group was heated and cooled through the model tests, and a three-dimensional finite element model of the energy pile group was established. The measured data and numerical results were compared and validated, and parameter analysis was conducted to study the thermo-mechanical response of the pile during the operation of a single pile for the energy pile group. The research results indicate that the results of numerical model and model tests are generally consistent. The bending moment was mainly concentrated in the upper part of the pile, its peak bending moment and inflection point are located 0.23 L and 0.8 L below the soil surface, and the horizontal displacement of the pile also decreased with the increasing depth. The horizontal load had a greater impact on the deformation characteristics of the pile, but the influence of temperature could not be ignored. As the temperature increased or decreased, the bending moment and displacement of the energy pile tended to increase. Compared with the only subjected to horizontal load, the increase in water temperature by 10 ℃ and 20 ℃ led to an increase in the Mmax (peak bending moment) of the energy pile by about 23.36% and 25.46%, and an increase in the horizontal displacement of the pile top by about 20.59% and 21.93% when the horizontal load and temperature variation were applied simultaneously. The decrease in water temperature by 10 ℃ and 20 ℃ resulted in an increase of approximately 23.48% and 24.39% in the energy pile Mmax (peak bending moment), and an increase of approximately 17.97% and 21.27% in the horizontal displacement of the pile top.
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Effect of excavation beneath for a new subway station on the shaft resistance of an existing pile

Huangfu, Yuan Chuanxu, Zhen Xuedong, Chen Kun, Xiao Jian

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During the construction of a new subway station beneath an existing running tunnel, the shaft resistance of the existing pile induced by the excavation may decrease and the bearing capacity of the pile may be affected. Presently, the computation theory of the shaft resistance for the existing pile induced by the excavation is not clear. Taking Shenzhen Metro Line 13 Gongming Square Station to cross the existing Line 6 project at zero distance as the background, the calculation formula of shaft resistance of pile induced by excavation under existing building is obtained by using the Mindlin stress solution. By comparing with the numerical simulation results, the correctness of the Mindlin stress solution is proved. The influence of parameter changes on shaft resistance of pile and unloading stress is analyzed. The results show that: when the depth of excavation increases, the total shaft resistance of pile decreases, and the ratio of side wall unloading stress to total unloading stress increases; when the excavation area increases, the total shaft resistance of pile increases, the ratio of side wall unloading stress to total unloading stress decreases. Therefore, when the excavation depth is deep, the excavation area is small, or the shaft resistance of side pile is considered, the influence of the side wall unloading stress needs to be considered.
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Dynamic Response Analysis of Shield Cutting Reinforced Concrete Pile Foundation

CHEN Yukang, Li Xinggao, MEI Jun, ZHANG Sheng, ZHANG Changshun, MING Fanlu

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In order to investigate the dynamic response characteristics during shield cutting pile process, the dynamic response induced by shield cutting pile impact load was solved by combining numerical simulation and theoretical analysis with the background of shield crossing group pile project of Nanjing Metro Line 10. Meanwhile, vibration sensors were installed on the cutterhead to monitor the dynamic response of the shield cutting pile. The results show that: (1) When the shield cuts reinforced concrete pile foundation at low speed of about 5 mm/s, the thrust and torque changes are small, and the thrust and torque show obvious hysteresis owing to the fact that the pile foundation is cylindrical and the cutting section increases slowly, and the peak thrust and torque are about 1.3 times and 1.25 times of the initial value. (2) The simulation results show that the rebar incision presents compression-tension fracture under the action of multiple cuts by the cutter. Under the action of impact loading, multiple dynamic response waveforms appear at the cutterhead bearing position with peaks close to 0.6g. (3) The measured data show that under the impact load, the time domain curve of cutterhead vibration acceleration shows several consecutive peaks with an interval of about 0.1 s and an amplitude of 0.5g, the measured impact response waveform is highly consistent with the theoretical solution and verified with each other. The waveform can be used as a typical characteristic of continuous cutting of steel bars by multiple cutters. (4) During the whole pile cutting process, the acceleration response Xrms, peak XP will be significantly higher, and the maximum intensity will be about twice as high as when cutting clay ground, and it will fall off rapidly after the pile cutting is completed. The relevant conclusions can provide a reference for the identification of shield cut pile status.
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Study on dynamic shear modulus of clay stabilized by lime-lignin

Zhou En Quan, Liuping, Zhangman, Lu Jianfei

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In order to study the dynamic deformation characteristics of clay stabilized by lime-lignin, a set of resonant column test was carried out on the stabilized clay with different confining pressures and lime-lignin contents, and the development law of dynamic shear modulus was analyzed. The results show that the maximum dynamic shear modulus and dynamic shear modulus ratio of clay stabilized by lime-lignin increase with the increasing of confining pressure. The maximum dynamic shear modulus and dynamic shear modulus ratio of 4%lime +4%lignin stabilized clay are the highest. Under a confining pressure of 300kPa, the maximum dynamic shear modulus of 4% lime+4% lignin stabilized clay is 17.3% higher than that of 8% lime stabilized clay and 185.4% higher than that of pure clay. Based on the shear strength parameters, the relative structure of stabilized clay was calculated and the relative structure of 4%lime +4%lignin stabilized clay is the highest. On the basis of Hardin formula, a characterization model of maximum shear modulus was established by introducing relative structural. The model has good accuracy and can provide a theoretical basis for evaluating the shear modulus characteristics of clay stabilized by lime-lignin.
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Vibration attenuation law of dynamic compaction and the effect of damping ditch parameters in a sandy foundation

CHENG Xuri, TONG Chenxi, WANG Xiaotaoi, FENG Yushun, ZHANG Sheng

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Dynamic compaction is a widely employed foundation treatment method, but the resultant surface vibrations can potentially lead to damage in nearby constructions. Therefore, it is crucial to determine appropriate safety distances and implement effective vibration absorption methods tailored to specific situations. Drawing from the dynamic compaction process at Fuzhou Changle International Airport, we conducted on-site tests to acquire essential data and subsequently performed simulations using the discrete element method. Our findings revealed that, under identical energy levels, lighter hammers result in higher soil velocities. Moreover, heavier hammers exhibit a broader influence and lead to a slower attenuation process compared to their lighter counterparts. Simulation results demonstrated that the attenuation process can be accurately modeled using hyperbolic functions, a conclusion substantiated by the results of our field experiments. Damping ditch calculations indicated that vibration velocities increase before the ditch and decrease thereafter. In accordance with relevant standards and calculation outcomes, the recommended safety distance for vibration in this field is 20 meters without a damping ditch, a distance that can be reduced to 10 meters with the implementation of a damping ditch. This research offers valuable insights and references for addressing related issues.
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Study on the mechanical response characteristics of debris flow accumulation under impact load

YU Yangyang, ZHAO Shizhong, TIAN Honglei, WANG Yang, LIU Jiashun, ZUO Jianping

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In order to study the mechanical response characteristics of debris flow deposits under the impact load of high-speed projectiles, the time-history curves of acceleration, velocity, displacement and stress of projectiles penetrating debris flow deposits were analyzed by means of impact load model experiment and numerical simulation. The characteristics of motion attitude, resistance and cavity in the process of projectile penetration were analyzed. The experimental results show that when the projectile penetrates the debris flow deposit, the displacement increases rapidly. With the instability of the motion attitude of the projectile in the debris flow deposit, the deceleration gradually increases. When the axial direction of the projectile is perpendicular to its motion direction, the contact surface is the largest, the resistance reaches the maximum, and the negative acceleration also reaches the maximum. During the penetration process of the projectile, the projectile arranges the debris flow deposit around to form a large cavity, and the velocity of the projectile decreases and the displacement increases slowly. During the penetration process of the projectile, with the increase of time, the projectile flips over, and finally the tail begins to move forward. The contact surface between the debris flow accumulation body and the debris flow accumulation body decreases, the resistance decreases, the acceleration decreases, the speed is relatively slow, and the curvature of the displacement curve decreases with the decrease of the speed. The research results can provide important reference and theoretical support for the design and safety assessment of high-speed projectiles in the mechanical response characteristics of debris flow deposits.
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Mechanism of Liangshuijing landslide deformation under the coupled effect of reservoir water level fluctuation and rainfall

CHEN Chao, WANG Yucheng, WANG Luqi, Fang Xiangwei, WANG Kai, WANG Ziqian

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Reservoir water level fluctuations and rainfall are primary contributors to the destabilization and damage of landslides in the Three Gorges Reservoir area (TGRA). Consequently, the investigation of the landslide deformation mechanism in the TGRA has gained significant attention since the implementation of the Three Gorges Reservoir. By utilizing recent monitoring data and focusing on the stepwise evolution of displacement, this study establishes a hydraulic calculation model for the Liangshuijing landslide. The research incorporates long-term data on reservoir water level fluctuations and rainfall to investigate the seepage field, stability, and displacement patterns under the combined influence of reservoir water level fluctuations and rainfall. Additionally, the study explores the intrinsic deformation mechanism of the Liangshuijing landslide. The results indicate that the seepage field in the front and back of the landslide is primarily influenced by the reservoir water level and rainfall, respectively, while the middle part is affected by the combination of both. The stability coefficient exhibits periodic changes corresponding to the rise and fall of the reservoir water level, and rainfall further diminishes the overall landslide stability. The surface displacement demonstrates an incremental trend, with a decrease in reservoir water level causing the displacement to increase incrementally, while an increase in reservoir water level tends to stabilize the displacement. Overall, the deformation of the Liangshuijing landslide is primarily caused by the reservoir water level fluctuations and rainfall, which subsequently impact the underground seepage field and hydraulic conditions, resulting in deformation. Generally, the current deformation is primarily concentrated at the foot of the slope, gradually extending towards the rear. The stabilization of deformation is observed in the middle and rear regions. Changes in the reservoir water level have a more pronounced impact on landslide deformation, and during years with greater fluctuations in the reservoir water level, it is crucial to enhance early warning monitoring of the deformation.
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Research On Intelligent Identification of Cable Tension with Damper Based on Deep Learning

jiangjiaping

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In order to solve the problem of difficulty and low accuracy in testing the cable tension with damper in practical engineering, an intelligent dentification method of the cable tension with damper based on IWPA-LCNN-LSTM is proposed. The dynamic response test of the cable with damper in practical engineering is carried out. Based on the data obtained from the test, a deep learning model that can intelligently identify the cable tension with damper is developed. The model takes the cable tension, length, line density, frequency, and order as the feature inputs. First, the hyperparameters in the LSTM neural network are adaptive optimized by using the IWPA. Then LKCNN-LSTM is used for training. The intelligent recognition of the cable tension with damper is realized. The average error between the recognized cable tension value on the test set and the actual cable tension value is only 2.024%, the mean square error value is only 0.0994%, the coefficient of determination is 0.9806, and the cable tension error is less than 5%. Finally, it is compared with the formula of cable tension calculation and other machine learning algorithms. The results show that this method can realize the intelligent and accurate recognition of the cable tension with damper and has a broad application prospect.
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New Advances in Condition Monitoring Technology for Reinforced Concrete Structures

ZHANG Fang, CONG Longyu, WANG Yuchen, YANG Qian, QIAN Yongjiu

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Monitoring the state of RC structures is an essential need to guarantee their performance level, which is both a traditional direction and a new development brought about by advances in other fields. This paper presents an overview of the new technologies in recent years for rebar corrosion monitoring and concrete durability monitoring techniques in reinforced concrete structures, mainly presenting (1) in terms of rebar corrosion monitoring, chemical monitoring methods such as half-cell and natural potential method, polarization resistance technique, current noise assessment method, and physical monitoring techniques such as ultrasonic monitoring method, physical imaging technique, and electromagnetism monitoring technique; (2) in terms of concrete condition monitoring, ultrasonic monitoring, digital imaging technology, damage evaluation index system research and other monitoring technologies based on the deterioration of concrete itself and monitoring technologies based on concrete cracks to assess the state of concrete; (3) in terms of sensors and signal processing technology, fiber optic sensors and other new sensor technologies. In the development of front-end technology in the state perception layer, the integration of human intelligence technology is a trend of future interdisciplinary development.
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Mechanical properties and crack model of non-through jointed sandy slate in triaxial unloading test

WANG Lehua, XU Jianwen, CHEN Can, GUO Jinfan, XU Xiaoliang

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During the excavation and unloading of underground chambers, the mechanical characteristics and crack propagation behavior of jointed rock formations are vital for project safety and stability. In this study at the Karala Hydroelectric Station in Sichuan, we conducted comprehensive tests on non-penetrating jointed sandy shale under triaxial loading and unloading conditions. We analyzed the mechanical properties and deformation characteristics under different stress paths, explored the applicability of various strength criteria, and investigated crack propagation mechanisms using fracture mechanics. The research outcomes have yielded the following insights:(1) As initial confining pressure increases, axial stress and strain at failure show an upward trend under different stress paths.(2) Compared to triaxial loading, unloading and jointed samples decrease load-bearing capacity. Unloading from axial stress to confining pressure increases cohesion (c) by 4.1% and decreases it by 30.4% during unloading from confining pressure to axial stress. Internal friction angle (φ) increases by 3.5% and 7.3% during axial compression, while jointed samples show a decrease of 32.9% and 53% in cohesion (c) and a decrease of 2.2% and 10% in internal friction angle (φ).(3) In terms of characterizing the strength properties of sandy shale throughout the loading and unloading process, the Mogi-Coulomb strength criterion outperformed both the Mohr-Coulomb and Drucker-Prager criteria. (4) The theoretical critical angle increases with confining pressure, and biconjoint samples exhibit higher values than intact ones. The theoretical critical angles range from 55° to 60° under different loading paths.
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Intelligent digital construction for complex frame-panel structures based on point cloud data and heuristic algorithms

LIAO Yue, LI Hantao, LIU Jiepeng, ZENG Yan, LI Lai''an, MA Xiaoxiao, CUI Na

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In the construction of large and complex frame-panel structures, it is difficult to measure the quality of the frame due to bending and torsion, which affects the panel installation. In addition, the traditional glass panel deepening design suffers from low efficiency and poor intelligence. Point cloud data (PCD) and heuristic algorithms provide a perfect solution for the status obtain of completed frame and intelligent of panel design. According to the Buildings of International Financial Forum located in Nansha District, Guangzhou city, the intelligent construction techniques for large-scale complex frame- panel structures based on PCD and heuristic algorithms were studied in this paper: Conversational modeling methods suitable for frames have been proposed in response to the design requirements of panels; The algorithms was proposed to extract the axis of the curved and twisted pip which have a polygon section to address the difficulty in skeleton geometry description; A unit-wise automatic extraction method has been proposed to improve the efficiency of panel partitioning; different strategies were used to generate panel layout schemes based on the Guillotine algorithm, and layout results were evaluated. The research show that the reverse modeling method can accurately obtain the frame model, the intelligent partitioning method for panel is simple and effective, and excellent cutting plans can be quickly obtained using heuristic algorithms. The results can be used as a reference for digital construction transformations of similar structures.
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Inner temperature field numerical analysis of reinforced-soil retaining wall under significant temperature fluctuation

Gaoyucong, Liuxuejun, Liuhuabei, Xiaochengzhi

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To investiage the changing regularity of temperature field of geogrid-reinforced soil (GRS) retaining wall under the significant temperature fluctuation, this study focused on a GRS retaining wall in Urumqi as the engineering context. Finite element models were constructed and employed to analyze the inner temperature distribution characteristics of the GRS retaining wall, taking into account the influence of solar radiation. The findings indicate a strong correlation between the inner temperature field of the GRS retaining wall and variations in environmental temperature, with the isotherm closely resembling a hyperbolic shape. Specifically, the temperature field within approximately 3-4.0 m behind the facing panels and about 2.0 m below the top surface of the GRS retaining wall can be classified as temperature-sensitive regions. Furthermore, the width of these temperature-sensitive regions expands in proportion to the thermophysical parameters. The utilization of filling material possessing enhanced thermophysical properties can effectively alleviate the average temperature gradient ?TV, however, the magnitude of the average temperature gradient ?TV predominantly depends on the rate of fluctuation in the external temperature. The maximum depths of frost exhibit an increase with the saturation of filling materials, with the most significant increment observed during the transition from a saturation level of 0 to 0.2. Furthermore, the findings of this study will serve as a significant point of reference for future investigations into the enduring stability of GRS retaining walls.
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Experimental study on physical and mechanical properties of simulated lunar regolith hardened by radiation sintering

HUA Jianmin, XIAO Chang, XUE Xuanyi, HUANG Lepeng

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The use of in-situ lunar resources to prepare structural materials is an important method of reducing the construction cost of lunar bases. On the basis of preparing simulated lunar regolith, the physical and mechanical properties of radiation sintering hardened simulated lunar regolith were studied. The results indicate that using volcanic slag as raw material, the preparation of simulated lunar regolith can be achieved through processes such as drying, impurity removal, crushing, and screening. The prepared simulated lunar regolith exhibits good similarity with real lunar regolith and existing simulated lunar regolith in terms of microstructure, particle size distribution, chemical composition, mineral composition, etc. Simulated lunar regolith hardening was achieved through radiation sintering, and the effects of sintering temperature and particle size distribution on the apparent density, sintering shrinkage, and mass loss rate of hardened lunar regolith were studied. The mechanical properties of hardened simulated lunar regolith were determined through monotonic compression tests, and the sintering temperature and particle size distribution of simulated lunar regolith had a significant impact on the mechanical properties of sintered hardened lunar regolith. Before the monotonic compression test failure, the specimen did not undergo significant plastic deformation. The elastic modulus did not change significantly, approaching the ideal linear elastic material. The variation patterns of elastic modulus, compressive strength, and ultimate strain of sintered hardened lunar regolith with different key parameters were discussed.
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Disease Detection method of Tunnel Portal in Plateau regions based on UAV images and Deep Learning

Che Bowen, Bao Weixing, Guo Qiang, Pan Zhenhua, Lu Hanqing, Yin Yan

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Aiming at the frequent diseases of tunnel portal built in the harsh environment of plateau region and the problems of low efficiency and high risk of traditional manual disease detection method, a disease detection method of tunnel portal in plateau region based on UAV image and deep learning was proposed. Firstly, an Unmanned Aerial Vehicle (UAV) was used to collect the disease images of a tunnel portal in the plateau region of Xinjiang, and a multi disease semantic segmentation dataset was constructed. Then, based on DeeplabV3+, an improved model TP-DeeplabV3+ was proposed, which used MobileNetV2 as the backbone feature extraction network to reduce the model parameters; Focalloss was used as the loss function to solve the problem of category imbalance in disease images; CA attention mechanism was uesd to improve the segmentation performance; and the disease quantification method was proposed. Experiment results show that TP-DeeplabV3+ can reach 88.37% and 94.93% of mIoU and mPA on the testset, and the model volume is reduced by 88.83%; The absolute error of the proposed disease quantification method for disease coverage rate is less than 0.3%, and the relative error is maintained below 7.31%. Compared with the traditional manual method, the proposed method can realize the intelligent detection of tunnel portal safely and accurately in plateau region.
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Multi-field information simulation method of reservoir landslide based on GeoStudio and FLAC3D mutual feedback

Yankun Wang, Tao Wen, Luqi Wang, Mingyi Hu, Mengxue Wei

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Accurately obtaining multi-field information of reservoir landslides under dynamic water action is an important foundation for landslide deformation mechanism and stability analysis. Although GeoStudio and FLAC3D are commonly used numerical software for simulating multi-field information in reservoir landslides, they still have several limitations. This paper proposes a multi-field information simulation analysis method of reservoir landslide fed by GeoStudio and FLAC3D. Time-varying seepage field of reservoir landslide under dynamic water is obtained by GeoStudio firstly, and an interface program is developed to realize the fast conversion of the GeoStudio model and seepage field to FLAC3D. Subsequently, incorporating the hydro-mechanical behavior of the geological materials and the principle of effective stress, the material parameters and initial stress of the FLAC3D model are modified to calculate the deformation of the reservoir landslide to realize a fast simulation of the multi-field information evolution process of reservoir landslide under dynamic water. The validity of the proposed method is verified by a large-scale physical model test of a reservoir landslide. The research results provide a feasible way for numerical analysis of the evolution mechanism and stability analysis of reservoir landslides under dynamic water.
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Vision-based Bridge Dynamic Deflection Measurement based on the Iterative Otsu Method under Low Light Conditions

Zhai Guohua, Tan Zhisen, Liang Yabin

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Currently, researchers employ LED targets combining with image thresholding method to address the issue that the visibility and resolution of structural surface characteristics decrease due to the influence of low-light environment, and finally induce the worse performance for the structural dynamic parameters measurement when using the vision-based technology. However, on the other hand, the complex ambient lighting and unfavorable weather in practical application will inevitably induce the negative effect for the vision-based measurement of the structural parameters. Therefore, in order to deal with this issue, a novel vision-based measurement method was proposed in this paper based on the iterative Otsu algorithm, in which the correct segmentation of the foreground spot and background image with the influence of strong light and fog interference can be realized by iteratively solving the image foreground threshold when combining with the iterative constraints of spot roundness and inter-frame area consistency, and fianlly the structural dynamic deflection can be obtained after collecting the spot center by the gray centroid algorithm. In this paper, the principle of the image thresholding segmentation based on the proposed iterative Otsu algorithm and the corresponding procedure for the structural displacement measurement were introduced at first. Subsequently, a cantilever beam specimen was employed to validate the feasibility and effectiveness of the proposed method, and finally the results demonstrate that the proposed method can realize the accurate identification of the structural dynamic deflection under low light conditions even with the influence of strong light and fog.
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Simplified Method for Thickness Design of Ecological Soil Covers in Northwest China

LI GUANGYAO, ZHAN LIANGTONG, JIAO WEIGUO, FENG SONG, CHEN YUNMIN

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Currently, the thickness design method for ecological soil covers used in Northwest China is based on the practice of non-humid regions in North America, which is complicated, involves many parameters, and fails to consider the different meteorological conditions between Northwest China and North America. To solve this issue, on the basis of the monsoon climate and the feature that the precipitation during the non-growing period of vegetation shall not exceed 20% of the total annual precipitation in Northwest China, as well as the water retention characteristics of ideal cover soils that the ratio of the field capacity to the wilting point K ≥ 1.44, the thickness design method for ecological soil covers used in Northwest China is simplified. Numerical program Vadose/W is utilized to analyze the hydraulic responses of the loess monolithic cover and the loess-gravel capillary barrier cover designed with the proposed simplified method in the year of maximum precipitation. The results indicate that the capillary barrier effect significantly prevents the migration of water from the loess layer to the gravel layer, resulting in the capillary barrier cover having better anti-seepage performance than the monolithic cover. The anti-seepage performance of the two covers decreases with the decrease in the ratio of the field capacity to the wilting point of the loess (i.e., K). When K ≥ 1.35, the two covers can meet the local anti-seepage requirements, thus preliminarily verifying the reliability of the simplified method proposed in this study. The proposal of the simplified method is conducive to the scientific design and application of ecological soil covers in Northwest China.
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Load-bearing performance test and finite element analysis of 3D printed steel fiber concrete circular arch structure under circumferential reinforcement

XIAJIAHUI, JIANGYOUBAO, ZHANGMINGLIANG, WENJUN, SHENTONG

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In order to enhance the mechanical properties of 3D printed concrete arc arch structure, this paper uses the methods of adding steel fiber and configuring steel reinforcement to investigate the effect of circumferential reinforcement on the mechanical properties of 3D printed steel fiber concrete arch structure. The appropriate steel fiber content was determined by mechanical properties tests under different steel fiber content. On this basis, two groups of 3D printed concrete arc arch structures were designed. By applying uniform load to the arch roof, load-displacement curve, strain change with load, cracking load and ultimate load of the arch structure were measured, and their deformation and failure laws were analyzed. Considering the influence of symmetric and asymmetric loading and the position of sectional reinforcement on the arch structure, the finite element calculation is carried out to further study its bearing performance. The results show that: (1) When the steel fiber content changes in the range of 0-3%, the compressive strength of 3D printed concrete in X, Y and Z directions increases first and then decreases, and the compressive strength in X, Y and Z directions corresponding to 2% steel fiber content is the highest; (2) The loading failure process of the two groups of arch structures is basically the same, and the ultimate bearing capacity of the arch structure under the circumferential reinforcement is about 37.5% higher than that of the plain concrete arch structure; (3) The finite element modeling method adopted is more accurate, and the error between the simulation results and the test results is less than 4%. The loading method and the position of section reinforcement have certain effects on the ultimate bearing capacity of the arch structure.
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Study on Weathering Mechanism of the Hariti Statue in Fowan of the Beishan Rock Carvings at Dazu

leiyu, liuhuan

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The Hariti Statue in Fowan of the Beishan Rock Carvings at Dazu has a very high cultural, historical and artistic value, but its weathering disease is serious, the statue of the long-term preservation is facing a serious challenge. In order to study the weathering mechanism of the Hariti Statue, this paper made a detailed investigation on the diseases of statues. The samples of weathered dust were collected from the surface of the rock mass of the Hariti Statue for X-ray diffraction (XRD) and ion chromatography (IC) analysis, which tested the mineral composition and the content and composition of the soluble salts. The meteorological parameters such as air temperature, relative humidity, rainfall and the concentration of atmospheric pollutants such as sulfur dioxide (SO2), nitrogen dioxide (NO2), 2.5-micrometer Particulate Matter (PM2.5), inhalable particles (PM10) in the study area were monitored for a long time by the Integrated Meteorological and Air Quality Monitoring Station. The results of disease investigation showed that dust and chalking flaking were the most important diseases to the stone and painting of the statue. XRD test showed that the mineral composition was dominated by quartz, plagioclase feldspar and gypsum. These mineral components have a large degree of weathering, and some components such as gypsum are susceptible to the decomposition under chemical weathering by various acids. IC analysis showed high content of Sulfate Ion (SO42-), Nitrate Ion (NO3-) and Chloride ion (Cl-), whose acidic corrosion and salinization accelerate the weathering and disintegration of the artifactual minerals. The results of environmental monitoring showed that the area was in the high humidity range of 70%~80%. The air temperature fluctuates greatly depending on the season, and the maximum temperature in the area of the statue is over 40℃ in summer. The warm and humid environment is easy to induce the weathering of stone cultural heritage, and when the temperature fluctuation is accompanied by the change of humidity, the risk of weathering will be increased. The air pollution in the statue area is serious, among which atmospheric particulate matters are the most important pollution factors. The chemicals in particulate matter along with acidic gaseous pollutants such as SO2 and NO2 will catalyze the erosion of minerals on rock surfaces. This study analyzed the influencing factors and potential mechanism of weathering of stone cultural heritage. The results can provide an important reference for the preventive protection of stone cultural heritage in hot and humid regions.
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Experimental study on solidifying landfilled municipal sludge using ferrous sulfate and cementitious materials

GUO Xiaojing, HUANG Zhiliang, CHEN Hui, HE Xiao, PU Hefu, YUAN Man, CAO Jianfeng

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In order to solve the problems of high water content and low strength of municipal sludge in the landfill, a synergistic method using ferrous sulfate and cementitious materials (such as lime, fly ash, and cement) was proposed to solidify landfilled sludge in-situ, and its reagent dosage was further optimized by the response surface method (RSM). The results showed that both ferrous sulfate and cementitious materials could reduce the water content of solidified sludge, but the reduction effect of lime and cement was more significant; the unconfined compressive strength (UCS) of solidified sludge increased with ferrous sulfate dosage and cement dosage, but first increased and then decreased with lime dosage, and basically did not change with fly ash; the quadratic polynomial model obtained by RSM could accurately predict the water content and UCS of solidified sludge, and it was verified that the relative error between the predicted value and the experimental value was less than 20%; under the constraints set in this study, the water content of solidified sludge in the recommended solution R7 (ferrous sulfate = 8%, lime = 6%, fly ash = 10%, and cement = 11%) reduced from 360.3% to 131.5%, and UCS increased from 0 to 317.0 kPa, which met the requirements of landfill disposal and mechanical entry.
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Safety assessment of wood structure in damaged state based on fuzzy analytical hierarchy approach

YANG Qingshan, ZHAO Jianbo, LIU Gang, WANG Juan

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Most of the existing ancient buildings are in service with injuries, and the internal damage state is complex and diverse. Meanwhile, the reinforcement and maintenance of the ancient buildings carried out by the later generations and the original damage have the opposite impact on the safety performance of the original structure. In order to realize the preventive protection of ancient buildings, it is necessary to quantify the damaged state of pure wooden structures of ancient buildings and the impact of repair measures on their safety state. Based on the survey and statistical data of the damaged state of various components of Feiyun Wood Pavilion in Wanrong, Shanxi Province, and combined with existing norms and engineering experience, this paper divides the damaged state of components in detail, establishes a four-level fuzzy hierarchical analysis model, and determines the weight value and judgment matrix of the load-bearing components and the damage types of components in the structure. The security state of Feiyun Wood Pavilion is evaluated by fuzzy analytical hierarchical approach. The results show that the fuzzy analytical hierarchy safety evaluation model established can reflect the damage state and the impact of repair measures on the safety state of Feiyun Wood Pavilion, effectively link structural evaluation with component evaluation, and verify that repair measures can effectively enhance the safety and stability of the ancient building structure. The model and method can be applied to the safety grade evaluation of multi-storey ancient wooden structures.
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Research on flexural performance of RC beams reinforced by TRC composite embedded prestressed CFRP bars

Luo Ziqing, Luo Junhui, Ning Jiejun, Yin Shiping, liu ziRui

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In order to study the flexural performance of reinforced concrete beams reinforced by TRC composite embedded prestressed CFRP bars, a four-point flexural load was carried out on 1 ordinary reinforced concrete beam and 5 TRC composite embedded prestressed CFRP bars, and the effects of slot size and diameter of CFRP bars on the flexural performance of the composite reinforced beams were analyzed. The test results show that the load increase of the composite reinforced beam is more obvious in each stage than that of the unreinforced beam. The ultimate load of the reinforced beam increases slightly with the increase of slot size and greatly with the increase of CFRP bar diameter. The flexural stiffness of the composite reinforced beam is obviously higher than that of the unreinforced beam. The increase of slot size and diameter of CFRP bars is not proportional to the increase of beam stiffness. The number of cracks in composite reinforced beams is obviously more than that of ordinary reinforced concrete beams and increases with the increase of slot size, but the diameter of CFRP bars has little effect. The ductility of the unreinforced beam is obviously higher than that of the reinforced beam. The ductility of the composite reinforced beam decreases with the increase of the diameter of the CFRP bar, and the increase of the slot size has no obvious effect on the ductility of the beam. Based on the calculation model of the cracking load of a single reinforced concrete beam proposed in the literature, a formula for calculating the cracking load of a composite reinforced concrete beam is proposed. The error between the calculated value and the test value is less than 6.5%, which indicates that the formula has good applicability.
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Acousto-optic characterization of splitting tensile damage of ultra-high per-formance concrete

CHEN Xudong, FENG Ziming, WANG Ningning, WU Wenwen, SHI Dandan, LUAN Jinjin

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In order to study the splitting tensile failure characteristics of UHPC (Ultra-High Performance Concrete), three different loading rates (0.1 mm/s, 0.01 mm/s, 0.001 mm/s) were used for splitting tensile loading. During the loading process, the digital image correlation (DIC) method was used to observe the crack evolution by non-contact deformation. At the same time, the acoustic emission (AE) technology was used to dynamically monitor the whole failure process of UHPC, and the failure characteristics of the specimen were analyzed based on the DIC strain cloud map and AE parameters. The results show that due to the incorporation of steel fibers, the brittleness of concrete is improved, and the post-peak load-displacement curve of UHPC decreases more gently without a sharp decline. The higher the loading rate, the higher the splitting tensile strength measured by UHPC, which conforms to the law of concrete rate effect. When the loading rate is increased from 0.001 mm/s to 0.01 mm/s and from 0.01 mm/s to 0.1 mm/s, the splitting tensile peak load is increased by 27.9 % and 28.5 % respectively. The digital image correlation method is used to measure the deformation of UHPC splitting tensile experiment, and continuous deformation data can be obtained, which can completely capture the development process of cracks. It is proved that DIC can well reflect the evolution process of cracks on the surface of specimens. The fracture mode analysis based on RA-AF can quickly and effectively determine the type of crack development in concrete. According to the analysis results, the crack types of UHPC splitting tensile experiment are mostly tensile cracks, and the proportion of tensile cracks in the total cracks increases with the increase of loading rate.
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An efficient time-varying reliability method based on AK-FORM method and dimension reduction method

Zhang Liang, Tang Yake, Niu Kai, Li Haoyu, Yu Shujun

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The PHI2 method is commonly used to perform the time-varying structural reliability analysis, and the calculation of outcrossing rate is the key to the method, to achieve sufficient accuracy it is often necessary to calculate the outcrossing rate at a large number of moments. However, for practical problems with complex limit state surfaces, the calculation of the outcrossing rate at each moment can be very time-consuming. To further improve the efficiency of PHI2 method, three strategies are proposed to be introduced in this paper to improve the efficiency of calculating outcrossing rate. First, the strategy without Cholesky decomposition is used to reduce the number of random variables, while the corresponding calculation of correlation coefficients is given. Then, the improved first order reliability method based on adaptive Kriging model (AK-FORM) is introduced to efficiently calculate the reliability index at each moment. Finally, the two dimensional integral is converted into one dimensional integral by using the dimension reduction method. The above three improvement strategies are combined with the PHI2 method, which forms an efficient time-varying reliability analysis method based on the AK-FORM method and the dimension reduction method, i.e., the K-PHI2 method. Meanwhile, only the strategy without Cholesky decomposition is combined with the PHI2 method to form the PHI2- method. The calculation results of numerical and engineering examples show that the PHI2- and K-PHI2 methods proposed in this paper have the same high accuracy as the PHI2 method, and both are better than the PHI2+ method (an improved method based on PHI2) in terms of accuracy; compared with the PHI2 and PHI2+ methods, the PHI2- method has a little improvement in efficiency, while the K-PHI2 method further greatly improves the efficiency of time-varying reliability analysis on this basis.
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Study on horizontal bearing characteristics of pile foundation in large thickness artificial fill foundation

liuderen

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The field test of single pile under horizontal load is carried out on the artificial fill foundation with large thickness. The load-displacement relationship, rotation angle and bending moment of the ground are measured, and the law of pile-soil interaction under horizontal load is revealed. The variation law of the proportional coefficient m of the horizontal resistance coefficient of foundation soil with load and displacement is also explored. The results show that the horizontal critical load of pile foundation is 480 kN, and after reaching the critical value, the horizontal displacement and rotation angle of pile foundation change suddenly. The bending moment diagram of the pile foundation shows a distribution pattern of " small at both ends and large in the middle ". The influence range of the bending moment along the depth is about 10 m, and the proportional coefficient of the horizontal resistance coefficient decreases exponentially with the increase of load and displacement. The results of m method are verified and improved by experimental data. It is found that the maximum displacement calculated by m method is close to the measured results. The calculation of bending moment when the load exceeds the critical load is quite different, compared to the correction coefficient function β, the m method is improved.……
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Effect of GCL overlap width on the Impervious Performance of Geosynthetic Clay Liners Composite Vertical Barrier Wall

Yang Shizhao, Xiao Chengzhi, zang nianyong, xie shiping, He shunhui

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GCL composite vertical anti-seepage wall is a new type of vertical anti-seepage and the wall composed of cement bentonite slurry wall and geosynthetic clay liners (GCL). The overlap of the two GCLs has a potential impact on the decline of anti-seepage and pollution control performance of such anti-seepage walls, and there is currently a lack of analysis of such effects in research. A two-dimensional pollutant migration model was presented in this study, and the comprehensive analysis of the effect of GCL overlap width, B2, permeability coefficient of GCL overlap area, kp, the thickness Lw and permeability coefficient kw of cement-bentonite wall on the transversal distribution of pollutant and critical GCL overlap width were carried out on the basis of numerical simulation method. The calculation results showed that the GCL overlap width affected the distribution mode in the GCL composite vertical barrier wall, and increasing the B2 but not reaching the critical GCL overlap width (corresponding to the moment of pollutant breaking through the GCL overlap width and non-GCL overlap range) caused to the increase of breakthrough time of GCL composite vertical barrier wall. Generally, pollutant concentration at the inlet of GCL overlap area is higher than that at the outlet of GCL overlap area, especially for the scenario of the smaller kp or Lw, or the greater kp. The decrease of kp or kw resulted in remarkable reduction of the critical GCL overlap width, whereas the breakthrough time tends to be the same as that in the GCL composite cut-off wall with non-GCL overlap width. In addition, to increase the thickness Lw of cement-bentonite wall caused the decrease of the required critical GCL overlap width. Moreover, a two-fold increase in Lw from 0.4 m to 0.8 m caused a 2.5 times increase of the breakthrough time of GCL composite vertical barrier wall.
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Field test and numerical simulation on thermal performance of a large-diameter bridge energy pile

ZHAO Zhipeng, WANG Zhipeng, Wu Di, CHEN Rong, KONG Gangqiang

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This study focuses on investigating the heat transfer characteristics of large-diameter bridge energy piles through field tests, aiming to examine the heat exchange rate and temperature distribution of a full-scale large-diameter bridge energy pile and surrounding soil. Additionally, three-dimensional numerical models of large-diameter bridge energy pile are developed and validated by comparing field measurements with simulation results. With the validated model, a parameter sensitivity analysis is conducted to explore the influence mechanism of convective heat exchange between bridge piers and surrounding air on the heat transfer characteristics of large-diameter energy pile. The results indicate that the heat exchange rate of large-diameter bridge energy pile can reach -222.28 W/m, which is approximately 1.5 to 3.9 times higher than that of conventional energy piles. However, the larger diameter of the pile leads to uneven temperature distribution across the cross section. Specifically, the temperature near the heat exchange tubes is significantly higher (around 3℃) compared to the temperature at the central axis position. Furthermore, it is observed that in low-temperature conditions, the convective heat exchange between bridge piers and surrounding air causes a decrease in the temperature of the pier, thereby increasing the heat exchange rate of the bridge energy pile under summer mode. When the surface of the pier transitions from natural convection (air flow rate of 0 m/s) to forced convection (air flow rate of 5 m/s), the heat exchange rate of the bridge energy pile increases by approximately 22 W/m.
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Analysis of wind-driven dynamic response of ice-covered long cross-bar transmission tower-line system in high altitude areas

FU Jianming, ZHANG Lijuan, MA Yidan, QI Yongjie, LIU Shiyuan, MENG Xiangrui, LIU Yuping, TIAN Li

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Transmission lines are susceptible to damage by a variety of disasters such as high winds and ice cover, which seriously threaten our energy security. At present, the study of wind and ice disasters on transmission lines is mostly focused on low altitude areas, however, many west-east transmission lines cross the vast plateau area, in which the long cross-burden transmission towers occupy a larger proportion, in order to ensure the safe operation of transmission lines in high altitude areas, this paper establishes a long cross-burden transmission tower-line system refinement model relying on a ± 800 kV UHV DC transmission project, based on the ice-covering conditions of the high-altitude areas, respectively, the establishment of the transmission towers and transmission lines of the ice-covered working conditions. At the same time, the wind load characteristics of high and low altitude areas are compared and analysed, taking into account the influence of environmental factors such as air density, topography and geomorphology in high altitude areas. Finally, based on the ice-covering conditions and wind load characteristics in high-altitude areas, the wind vibration response analysis of the long crossbar transmission tower-line system was carried out. The results show that the wind profile at high altitude is relatively gentle, the displacement response at the cross-burden of the long cross-burden transmission tower-line system is larger than that at the top of the tower, and the maximum displacement response of the structure under ice and wind loads occurs at the midpoint of the cross-burden end.
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Research on the shear behavior of rib-treated interface between ultra-high performance concrete and normal Concrete

WANG Peng, You Xuehui, SHI Qingxuan, TAO Yi

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To investigate the interfacial shear performance between ultra-high performance concrete (UHPC) and normal concrete (NC), 13 UHPC-NC direct shear specimens were designed and fabricated. Through push out tests, the influence of UHPC rib width, height, and spacing on the interfacial failure mode and shear bearing capacity were discussed. Furthermore, a finite element model of the UHPC-NC specimens was established using ABAQUS, and parameter analysis was conducted. The results indicate that the failure modes of the ribbed UHPC-NC interface mainly include: complete interface failure and UHPC ribs sheared off; partial interface failure and partial failure of NC embedded between UHPC ribs; partial interface failure and complete failure of NC embedded between UHPC ribs. The specimens with rib widths of 10 mm primarily exhibit the first failure mode, while specimens with rib widthsof 15 mm and 20 mm correspond to the latter two failure modes. Additionally, as a whole, the shear capacity and slip of the interface gradually increase with the increase of rib width and spacing, demonstrating better ductility. When the rib width is 20 mm, increasing the rib height helps to improve the interface load-carrying capacity. However, as the rib height increases, the effectiveness of load enhancement significantly decreases.
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Virtual Static Load Test Method for Stiffness Evaluation of Main Girder of Long-span Cable-stayed Bridge under Normal Traffic

Qi Xingjun, Yang hongchao, Zhang Bin, Sun Peng, Cao Sanpeng, Guo Dongmei

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In order to investigate the feasibility of virtual static load test method to evaluate the stiffness of the main girder of a large span cable-stayed bridge, a cable-stayed bridge was subjected to static load test and modal test under environmental excitation. Based on the modal parameters identified under the environmental excitation, the modal expansion of the measured vibration pattern of the cable-stayed bridge was carried out by applying the kriging interpolation method to predict the modal deflection of the span section of the cable-stayed bridge under the static load test, and compare the measured static deflection with the measured static load. The deflection calibration coefficients under virtual static load were calculated to evaluate the stiffness of the main girder of the cable-stayed bridge. The results show that the modal test under ambient excitation can accurately identify the modal parameters of the bridge; the relative error between the first four orders of vibration patterns predicted by the kriging interpolation method and the measured static load deflection was less than 10%, which meets the requirement of engineering accuracy and indicates the engineering accuracy of the modal deflection applied to large span cable-stayed bridges; the difference between the virtual static load test method and the static load test obtained deflection The difference between the virtual static load test method and the static load test deflection coefficient was small, and the evaluation results were less than 1.0, which indicated that the main girder of the cable-stayed bridge was in good bearing condition, fully demonstrating the feasibility and effectiveness of the virtual static load test method in evaluating the stiffness of the main girder of large-span cable-stayed bridge under normal traffic.
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The mechanical properties of solidified oil-contaminated soil and the evolution of contaminant migration under leaching function

Limin, Yuhemiao, Lihui, Zhaomoyan

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Clarifying the mechanical properties of solidified oil-contaminated soil and the evolution of contaminate migration and diffusion under environmental effects is a key prerequisite for promoting the reuse of contaminated soil projects. Lime and fly ash with a low-carbon concept were selected as solidification materials, combined with the leaching test and COMSOL Multiphysics software, the control of the solidification effect on oil migration under leaching environment was evaluated macroscopically by oil content after leaching, and the mechanical stability under seepage was evaluated by soil strength and deformation. The results indicate that the solidification of lime fly ash can solve the problem of contaminant migration and diffusion or even a large number of migration under the leaching effect of contaminated soil, and achieve good control of the migration of oil contaminants in soil. The oil content at the interface of solidified contaminated soil under the action of seepage leaching is always close to the initial oil content setting state, and the change rate mobility is only 1.35 % ~ 2.76 %. The variation range of mechanical parameters of solidified contaminated soil under leaching is positively correlated with confining pressure and contaminant concentration, but only fluctuates within 10 s of initial stress and then the strength value is stable at 5.77×104 ~ 6.07×104 N / m2, and the maximum fluctuation value of displacement is 1.73×10-3 ~ 6.46×10-2 mm. The mechanical stability of solidified contaminated soil is good, and the safety factor (Fs) is more than 10. Lime fly ash solidified oil contaminated soil can take into account both environmental and engineering requirements, and has the potential for engineering reuse.
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Study on prediction model for horizontal axis deviation of segment during construction stage of small curvature radius shield tunnel

Zhu Chunzhou

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In order to investigate the law of horizontal axis deviation of segments caused by small curvature radius shield tunnel construction and prevent adverse phenomena such as segment misalignment and damage, this study is based on a modified longitudinal equivalent continuity model and establishes a prediction model for horizontal axis deviation of segments during the construction stage of small curvature radius shield tunneling by constructing the Winkle foundation beam deflection differential equation under the condition of small curvature radius. And the engineering applicability of the prediction model was verified based on the shield tunnel project of Nanchang City's urban rail transit Line 3. The results show that the prediction results of the model in this study fit well with the on-site monitoring results, meet the requirements of the error limit allowed by engineering experience, and the relevant laws are basically consistent. It can effectively solve the problem of calculating the horizontal axis offset of tube sheet during the construction of shield tunnel under the condition of small curvature radius, which provides an effective theoretical guidance and reference for the smooth construction of similar tunnel projects.
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Influence of loading medium on mechanical properties of geomembrane bulging deformation

lizheng, liwanglin, wangwansheng, yuhairui, xuexia

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In order to find out whether the loading medium has an effect on the mechanical properties of the expansion deformation of the geomembrane, the HDPE geomembrane with three thicknesses of 0.2mm, 0.3mm and 0.6mm were selected as the research object, and the air and water were used as the loading medium respectively. The spherical bulging deformation test under the ring constraint was carried out, and the following conclusions were drawn : (1) The loading medium has a great influence on the bursting pressure and bulging height of the geomembrane during the expansion of the geomembrane. The bursting pressure under the water expansion is about
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Experimental study on the bonding performance of GFRP ribbed ribs and simplified constitutive model

ZHANG Wangxi, LIU Xin, HU Binbin, XIANG Zhenhang, YUAN Chao, YI Weijian

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To investigate the bond performance between glass fiber reinforced polymer (GFRP) ribbed bars and concrete, and to improve the convenience of using the existing constitutive model, 14 sets of specimens were prepared for beam-end tests, The tests aimed to explore the influence of concrete strength, thickness of cover, stirrup configuration and GFRP ribbed interaction on the bond performance. The tests were conducted using displacement-controlled loading, and loading force, free end slip value, and loading end slip value were recorded, The failure mode of the bond interface was observed, and a simplified bond-slip constitutive model was proposed based on the test results. The results showed that the beam-end tests mainly resulted in pull-out failure and splitting failure; The slip value of the bond-slip curve was related to the rib spacing, and the peak spacing was essentially consistent with the rib spacing; Concrete strength and Configuration stirrup would affect the failure mode and damage degree of the bond interface, thereby affecting the bond slip performance; The increase in thickness of cover had a beneficial effect on the bond slip performance within a certain range; The results of the second pull-out test showed that there was a mutual influence on the bond performance of GFRP ribbed bars in the specimens. The simplified bond-slip constitutive model was able to accurately fit test data and further enhance the practicality of the constitutive model.
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Study on the influence of screw height on vertical bearing characteristics of threaded pile

xu li na, Qi Chenhui, Zheng Junjie, Huang Zhanfang, Sun Shuang

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In order to find out the influence of screw height on the bearing characteristics of threaded pile and soil around the pile under vertical load, this paper studied the influence of different screw height on the bearing performance of pile, soil failure characteristics around the pile and soil displacement field around the pile through indoor half-surface model pile test combined with digital image correlation technology (DIC). The Abaqus numerical simulation method was used to verify the results of the model test, and the value range of screw height was extended. The law of the ultimate bearing capacity and material utilization ratio of screw pile and the distribution of soil stress field around the pile were analyzed. The results show that the bearing capacity of pile is increased, the influence range of the soil displacement around the pile gradually is increased and the development of shear failure of soil around the pile can be delayed with increase of the screw height. As the settlement of the pile body increases, the load on the pile top gradually evolves from being borne by the pile side resistance to being borne by the pile end resistance. Although increasing the screw height can enhance the ultimate bearing capacity of the pile, there is a peak in the utilization rate of the pile body material.
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Study on influencing factors of dye wastewater by catalytic oxidation with Mn/GAC-ozone micro-nano bubbles

Wei Jie, Zhu Yanli, Wang Shujin, Wang Ruonan

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The catalytic oxidation process combined with micro-nano bubbles is a new method to treat dye wastewater, which solves the problem of difficult biodegradable organic pollutants and reduces the chroma of dye wastewater, and has a good application prospect.Taking simulated cationic dye wastewater as the research object, with Manganese nitrate/activated carbon (Mn/GAC) as catalyst,the cationic dye wastewater was treated by ozone catalytic oxidation process combined with micro-nano bubbles aeration technology. Based on the determination of the initial concentration of cationic dye wastewater and ozone concentration, orthogonal tests of catalyst dosage, initial pH value of wastewater and initial wastewate temperature carried out, and their influence on the treatment effect of cationic gold X-GL dye wastewater was investigated. Experimental results show that catalytic oxidation of micro-nano bubbles can have a good effect on the chroma removal of cationic gold X-GL dye wastewater. When the amount of catalyst is 3.5 g/L, the initial pH value is 9.4, and the initial temperature is 23.6℃, the verification experiment is carried out under this optimum combination condition, and the experimental results show that the best chroma removal rate is 95.6%. It shows that the treatment of dye wastewater by this process has achieved the expected effect and has certain guiding significance.
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Removal of heavy metal complexes by UV/Fe(Ⅲ) process: Performance and mechanism

DING Yuxin, YANG Zhengheng, MA Xiaoming, YU Jin, JIN Qinghai, He Di

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UV/Fe(Ⅲ) process is a new combined process for treating heavy metal complexes. This process first releases free metal ions through the replacement of Fe(III), then, it degraded the organic ligands via UV irradiation, and finally, heavy metals were removed by alkaline precipitation. In this study, heavy metal complexes, Cu(Ⅱ)-EDTA and Ni(Ⅱ)-EDTA, were removed by UV/Fe(Ⅲ) process. Through the comparison of removal effects and mechanism analysis, the internal mechanism of the difference in removal effects of the combined process was described, and the corresponding optimization scheme was proposed. The results showed that the removal efficiency of Cu(Ⅱ)-EDTA and Ni(Ⅱ)-EDTA was quite different, and the removal rates of Cu and Ni were 70% and 41%, respectively. The main reason for the difference in removal efficiency between Cu(II)-EDTA and Ni(II)-EDTA was determined through high-performance liquid chromatography (HPLC), spectrophotometric analysis, and benzoic acid (BA) probe experiments, showing that Fe(III) had a noticeable difference in displacing Cu(II) and Ni(II), with replacement rates of 85% and 22%, respectively. Optimal Fe(III) dosages and reaction temperatures were separately optimized for the Ni(II)-EDTA replacement process. The results showed that the reaction temperature optimization can significantly improve the Fe(Ⅲ) displacement efficiency on Ni(Ⅱ)-EDTA. When the reaction temperature was increased to 35℃, the removal efficiency of Ni was increased from 41% to 60%. The reaction temperature is very important for the removal of Ni(Ⅱ)-EDTA by UV/Fe(Ⅲ) process, proper heating is helpful to increase the replacement rate and further improve the removal efficiency.
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Experimental study on fatigue performance of external joints in steel truss web-concrete composite box girders

TAN Yingliang, ZHU Bing, CUI Shengai, BI Xinyu, ZHANG Zhen, LU Baojie

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Two joint models with a scale of 1:3 were fabricated and fatigue tests were carried out to investigate the fatigue performance of steel truss web-concrete composite external joints and verify the reliability of the new structure applied to high-speed railway bridges. The fatigue damage mode, load-displacement relationship, and load-strain curve of the composite external joints were investigated, the fatigue force characteristics of the external joints under different stress amplitudes were investigated. The experimental results showed that the fatigue life of the composite external joint exceeds 2.51 million loading cycles under the design stress amplitude, the joint is not damaged, the stiffness is not reduced, and the fatigue resistance performance meets the requirements. Under the action of 1.4 times design stress amplitude, the measured fatigue life of the external joint is 1.4 million times. The fatigue damage mode of the external joint is the cracking of the exposed gusset plate on the tensile side, and the critical detail of composite external joint is the welding detail which connecting the exposed gusset plate and the stiffening plate. The fatigue crack causes the stress redistribution in the gusset plate, the strain in the gusset plate above and below the crack is reduced by 81% at most, and the strain in the gusset plate near the crack is increased by 33% at most. According to the S-N curve obtained by the one-point method, the fatigue life of the composite external joint corresponding to the design stress amplitude of 53.2MPa is 4.36 million times, which is 2.18 times of the design life.
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Verification of track structure modeling and analysis of damage parameters of spring isolators

fuweiqing, dihuilin, zhaoliang, wangjian

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In urban rail transit structures, spring vibration isolators are typically installed beneath floating slabs to reduce vibration transmission and ensure stable and safe train operation. However, due to the long-term and repetitive loading of trains, the spring isolators may become damaged or suspended, making them difficult to detect during inspections as they are concealed components. A vehicle-track coupled model was established using ABAQUS finite element software, and the measured vibration data of a certain section of the Shenzhen Metro floating slab was selected to validate the model. The uniform design method was used to conduct parameter experimental design on different damage quantities, degrees, and locations of the spring isolators. The quantitative impact of each damage parameter on the vibration response of the floating slab was obtained through model simulation and calculation. The calculation results show that the location of damage to the spring isolator has the greatest impact on the acceleration and displacement of the floating slab, with influence weights of 50% and 49.3%, respectively. Next is the damage quantity, with influence weights of 28.4% and 27.9%. Lastly, the damage degree has an influence weight of 21.6% and 22.8%. The research results can provide reference for the design of vibration isolators in urban rail structures and the safety monitoring of train operations.
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The Influence of Cyclic Temperature Variation on Mechanical Properties of Grotto Sandstone under Triaxial Stress Condition

JiangSiwei, WangChenglong, LiuDongsheng, GuoYachen, ZhangWengang, CHENHuili

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The rock mass of the grotto temple has been affected by cooling and heating for a long time, which will lead to the change of the mechanical properties of the rock mass and affect the protection of the grotto temple. In this paper, the Dazu Rock Carving sandstone in Chongqing was taken as the research object, and the mechanical properties of the sandstone were studied through triaxial compression tests. The experimental process involves multiple conditions such as different heating-cooling cycle times, different durations of high and low temperatures, and different cooling methods. These test conditions were designed to analyze the influence of temperature changes on the peak stress and strain, elastic modulus, internal friction angle, cohesion, and failure mode of Dazu Rock Carving sandstone. The results could be found that: (1) The mechanical properties of sandstone weakened after multiple heating-cooling cycles. The values of strength, elastic modulus, cohesion, and internal friction angle decreased at different degrees. (2) The peak strain of sandstone increased after multiple heating-cooling cycles. (3) The failure mode of sandstone under triaxial compression was mainly shear failure with a single shear plane, while the failure mode became complex after multiple heating-cooling cycles, which resulted in the conjugated shear failure of “Y” type. (4) Confining pressure could improve the mechanical properties, which increased the strength and elastic modulus of the sandstone samples.
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Study on Mesoscopic Fracture Simulation of Dense Sandstone Based on Acoustic Emission

Li Gao, Wu Xuefeng, Yang Xu, Feng Jiaxin

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This paper aims to investigate the mesoscopic fracture mechanisms of sandstone under triaxial compression. We conducted indoor triaxial compression tests of sandstone and integrated the Grain-Based Model (GBM) and moment tensor theory to simulate the development characteristics of internal cracks, acoustic emission events, and fracture strength in sandstone. Derive the derivation process of microcracks and the characteristics of acoustic emission response in sandstone, and comprehensively analyze the spatiotemporal evolution process of cracks and acoustic emission events at the micro scale. The results indicate that microcracks are randomly distributed in the sandstone sample during the initiation stage of fracture under triaxial compression, and the displacement field shows a horizontal layered distribution. As the load increases, the number of microcracks increases, penetrates gradually into two macroscopic cracks, and shifts the displacement field to a significant heterogeneity. The cracks in the incubation periodshow slow development, andCracks grow at extremely high nonlinear rates. The order of crack development follows a sequence of intergranular tensile cracks, intergranular shear cracks, intragranular tensile cracks, and intragranular shear cracks. The simulation analysis revealed that the majority of internal cracks triaxial compression (83.2%) are tensile cracks resulting from tensile failure. The number of acoustic emission events in the samples has a negative exponential correlation with the number of cracks, and a single acoustic emission event generates 75.60% of microcracks. Finally, the analysis of acoustic emission events, the number of microcracks, and the fracture strength indicates that the three factors approximately follow a normal distribution.
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Technology status and development trends of concrete-steel hybrid towers for wind turbines

WANG Dan, XU Jun, HE Guangling, WU Qiang, LI Yuxiang

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In order to exploit wind energy resources in low wind speed and high shear areas, the hub height of wind turbine needs to be increased. There are three main engineering solutions of high tower, namely all-steel towers, all-concrete towers, and concrete-steel hybrid towers (hybrid towers). Firstly, this paper compares the technical characteristics of the three towers. The results show that the use of hybrid tower combines the advantages and overcomes the disadvantages of both all-steel and all-concrete towers, and is the preferred solution to meet the challenges of high tower. Secondly, this paper reviews the development history and research status of hybrid tower technology around the subject of tower types (chamfered square, cone, chamfered triangle, kidney shape, polygon, self-lift), and summarizes the domestic technological development of hybrid tower into three development stages and three technology genres. Thirdly, this paper introduces the domestic and international industry standards of hybrid tower, and outlines the existing key technology researches of improving the performance, optimizing the cost, shortening the construction cycle and health monitoring of hybrid tower. Finally, this paper summarizes the problems and challenges in the research of hybrid tower technology, including: structure unification, adoption of sub-model analysis techniques, reliability studies, upgrading of old hybrid towers and research on ultra-high hybrid towers, which provide references for new product development. With high stability, long service life and low construction cost, hybrid towers can meet the development requirements of large wind turbine.
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EFFECTS OF CORNER-BRIDGE FLOW ON CAPILLARY PRESSURE-SATURATION CURVE IN POROUS MEDIA

Wang Guan-Xiong, Hu Ran, Lan Tian, Chen Yi-Feng

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The capillary pressure-saturation curve is the basis for predicting multiphase flow in porous media. As the saturation of the wetting phase decreases, flow through the meniscus and liquid bridges becomes the main mechanism for displacement. However, the understanding of how meniscus and liquid bridges control the capillary pressure-saturation curve is still limited. In this study, we constructed a microfluidic visualization experimental platform and conducted quasi-static drainage experiments in six different microfluidic systems with varying pore structures and roughness. Through the experiments, the phenomena of meniscus-liquid bridge were observed and the influence of this phenomenon on the capillary pressure curve was quantified. The experimental results show that the meniscus-liquid bridge phenomenon mainly occurs at lower saturations and leads to a reduction in the residual saturation of the wetting phase by 0.21 to 0.32. The occurrence of the meniscus-liquid bridge phenomenon is closely related to the wettability of the porous media, where rough solid surfaces decrease the contact angle of the wetting phase, making the meniscus-liquid bridge phenomenon more likely to occur. The impact of the meniscus-liquid bridge is positively correlated with the number of liquid bridges, and as the porosity and heterogeneity decrease, the meniscus-liquid bridge phenomenon becomes more significant. This study reveals the influence of the pore-scale meniscus-liquid bridge phenomenon on the capillary pressure-saturation curve, which is of significant importance for predicting multiphase flow.
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Research on preparation and thermal activation effect of geopolymers based on burnt coal cinder

Li Mnegke, Bao Shenxu, Zhang Yimin, Huang Muyang

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To address the issue of low activity and challenging treatment of burnt coal cinder, the preparation technology and calcination effect of geopolymers based on burnt coal cinder were investigated, with the concept of low carbon and environmental protection as the core. The influence of calcination temperature, activator dosage and liquid-solid ratio on the compressive strength of geopolymers based on burnt coal cinder was investigated by single factor tests and the optimal mix ratio was subsequently determined. By utilizing X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), the hydration products and micromorphology of geopolymers were studied. Revealing mineral phase changes of calcination and geopolymerization process and clarifying the mechanism of strength enhancement. The results indicate that the combined activation method of the main calcium oxide and the auxiliary trisodium phosphate dodecahydrate (TSPH) was successfully employed to prepare the geopolymers with a compressive strength of 34.5 MPa at 28 d. The alkaline environment and nucleation sites provided by calcium oxide, along with the phosphate radicals supplied by TSPH, all contribute to the dissolution of active components in burnt coal cinder and formation of complex gel phases, which is an important source of compressive strength of geopolymers. Moreover, under calcination temperatures of 1000℃, burnt coal cinder lacks the thermal activation property of solid wastes such as coal gangue and fly ash, and high temperature calcination diminishes its chemical reactivity.
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Comprehensive analysis on causes of flood disaster in megacities - A case study of Chongqing

ZHANG Wengang, WANG Yunhao, HU Qingfang, SUN Weixin, JIN Junliang

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In recent years, extreme meteorological and hydrological events tend to be more and stronger, the frequent occurrence of flood disasters in a rapidly evolving environment has brought severe challenges to both social and economic development. This study concentrates on the Chongqing, one of two principal cores within the megacities of western China, part of the Chengdu-Chongqing urban agglomeration. This city's terrain, predominantly hilly and mountainous, together with its proximity to upstream rivers and the backwater of the Three Gorges Reservoir area (TGRA), highlights its exposure to the threat of flood disasters. This study focuses on Chongqing's historical flood disaster events to assess the current state of flood prevention and disaster reduction efforts within the city. We further analyze the impact of various factors – including hydrology, geography, topography, urbanization, and meteorological conditions – on both the frequency and intensity of flood disasters in Chongqing. Alongside these causal factors of flood disasters, we further delve into the analysis of Chongqing's disasters – forming environment and the entities that bear these disasters. Finally, countermeasure suggestions for flood management in the central city of Chongqing are presented. The findings indicate that the occurrence of flood disasters in Chongqing is influenced by a myriad of factors, and the special location and the characteristics of the mountain city determine the difficulty of flood prevention and management in Chongqing. Notably, the city's complex terrain and numerous rivers meet the conditions conducive to flood disasters. Given the evolving circumstances brought about by meteorological hydrology and socio-economic developments, it is imperative to proactively reassess and optimize Chongqing's urban flood disaster prevention system. This should be done in accordance with the unique flood disaster characteristics that have emerged following the completion of the TGRA and the current flood control and waterlogging prevention capacity of the urban area.
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Study on Flexural Performance of Prestressed RC-UHPCComposite Box Girder

XIA Zhanghua, JI Bangchong, YANG Yang, LIN Shangshun, LIN Jianfan, ZHAO Jinbing

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In order to explore a new type of composite box girder with light lifting weight, convenient construction and high durability, a new type of prestressed RC-UHPC composite box girder with ultra-high performance concrete (UHPC) as web and bottom plate and plain concrete (RC) as top plate was designed and fabricated. Flexural tests and finite element analysis were carried out to investigate the failure mechanism and failure mode of the specimens. The results show that: the failure mode of the specimen is suitable reinforcement failure, which shows that the RC of the top slab in the pure bending section is crushed after the yield of the longitudinal tensile reinforcement and the fracture of some prestressing reinforcement; the tensile strength of UHPC and the reinforcement ratio of prestressing tendons have a greater influence on the flexural strength; the longitudinal strain of the web of the specimen is basically consistent with the assumption of a flat section in the height direction. Combined with the theoretical analysis, the formulas for calculating the flexural strength were proposed. The ratio of the calculated value to the test value and the calculated value of the finite element is 1.014 and 0.960, respectively, which has a high calculation accuracy. This study can provide a theoretical basis for the promotion of prestressed RC-UHPC composite box girder in practical projects and the formulation of specifications.
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Research progress on durability of concrete under influence of internal curing

luodaming, lifan, niuditao

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Concrete exhibits exceptional mechanical properties and durability. However, conventional curing methods are ineffective in addressing the issues of autogenous shrinkage and cracking during the early stages. Internal curing technology effectively enhances the internal moisture distribution of concrete, mitigates shrinkage cracking, and improves durability. This paper investigates the internal curing mechanism of concrete and analyzes its influence on the durability of concrete. By incorporating pre-wetted lightweight aggregates or super-absorbent polymers into the concrete, water can be released as the moisture surrounding the aggregate decreases. This process fills the unsaturated pores in the concrete and increases the meniscus radius of the pore solution, thereby achieving internal curing. Internal curing promotes cement hydration around the aggregate, improves the compactness of the interfacial transition zone; alleviates concrete cracking caused by self-desiccation, and enhances cracking resistance. Moreover, it obstructs the transmission path of corrosive media, improves concrete permeability, and enhances corrosion resistance against ions, gases, and other corrosive agents. After water release, the internal curing material creates a substantial number of pores in the concrete. These pores aid in releasing the expansion pressure resulting from the freezing of the concrete pore solution, thereby improving frost resistance. Additionally, the pores of lightweight aggregate provide space for the deposition of expansive gel, reduces the occurrence of alkali-aggregate reaction. This paper summarizes the advantages of concrete internal curing technology and looks forward to its future application, providing a reference for further research and field application of this technology.
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Indoor model test study of TBM cutter penetration load evolution rules assisted by pre-cutting slit

Jiang Yalong, Xu Pengchuxuan, Zeng Jianjun, Xu Changjie, Xiong Fuyang

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：Based on indoor model test study of TBM cutter, the evolution characteristics of highly abrasive granite sample penetration load under different confining pressure conditions were studied by three different rock-breaking modes (complete rock breaking, same-trajectory rock breaking and different-trajectory rock breaking). Focusing on revealing the changes of penetration load-penetration depth characteristic curve, peak load and maximum drop amplitude. Obtaining the force characteristics of TBM cutter under different rock-breaking modes and confining pressure conditions. The results show that: (1) The penetration load-penetration depth characteristic curve of the low confining pressure group in the high confining pressure group falls first, The drop amplitude is small, but its corresponding penetration load is not a peak load. while the initial drop load in the low confining pressure group is a peak load with a large drop amplitude (2) At medium to high confining pressures of 10-15 MPa , The peak load and penetration load have the smallest maximum drop amplitude, which is the optimal excavation environment for TBM by pre-cutting slit.(3) Under low confining pressure condition, the different trajectory rock-breaking mode can effectively reduce the TBM penetration load compared with the same trajectory rock-breaking mode. However, under each confining pressure condition, the rock sample with the same trajectory rock-breaking mode has wedge failure, and its maximum drop amplitude is the smallest, which can reduce the impact load of the cutter, and reduce the cutter wear.
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Simplified method for calculating the pipeline nonlinear deformation caused by tunnel undercrossing

YIN Xin

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The construction of urban subways and underground passages inevitably involves undercrossing existing municipal pipelines, which can cause pipe deflection and threaten pipeline safety. Most of the existing prediction theories for pipeline deformation caused by tunneling use elastic foundation models such as the Winkler model and the Pasternak model, which lack consideration of the nonlinear interaction between soil and pipelines. To further consider the nonlinear deformation of the soil, a simplified calculation method for predicting the nonlinear deformation of pipelines caused by tunneling was proposed. Firstly, a nonlinear foundation model was introduced, and the existing municipal pipeline with rigid joints was regarded as a continuous beam on the nonlinear foundation. Secondly, the ground displacement at the axis of the pipeline caused by single-line and double-line tunneling was calculated respectively, using the Peck empirical formula and the modified Peck empirical formula that considers the tunnel construction sequence. Then, assuming that the pipeline and soil deformation are coordinated, the differential control equation for pipeline deformation caused by tunneling was established, and the deformation solution of the pipeline was obtained using finite difference method and Newton iteration method. Finally, the rationality and applicability of the proposed method were verified by comparing its results with monitoring data from a centrifuge experiment and two engineering cases. The results show that the proposed method can effectively predict the longitudinal deformation of existing municipal pipelines with rigid joints caused by tunneling well in both sandy and clayey soil layers. It can also predict the pipeline deformation caused by twin-tunnel undercrossing after considering the effect of tunnel construction sequence. Compared with other foundation models such as the Winkler foundation, Pasternak foundation, and Kerr foundation, the proposed method has a better agreement trend with the measured data. This research provides a new prediction method for predicting the deformation response of municipal pipelines caused by tunneling and can provide theoretical support for the safety assessment and deformation prediction of municipal pipelines.
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Study on acoustic emission response characteristics and early warning of prefabricated hole tuff failure

zouhaiyun, xuxiaojing, xuwangliang, songzhanping, zhangzekun

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Uniaxial compression test and acoustic emission test were carried out on tuff with double round holes of different rock bridge lengths to obtain the acoustic emission parameters of rock deformation and failure process. The influence of rock bridge length on acoustic emission response characteristics was studied, and the early warning precursor information was analyzed based on acoustic emission characteristic parameters. The results show that the acoustic emission parameters change periodically with time, and there are obvious abnormal response characteristics before rock failure. AE energy changes from group earthquake type to solitary earthquake type with the increase of rock bridge length. AE ringing count has experienced quiet period, active period and sudden increase area. AE RA/AF value is sensitive to local small crack propagation. AE b value has experienced rising period, fluctuation period and falling period with time, and the overall trend is decreasing. Each parameter of AE has the precursor of rock failure. The AE cumulative energy, AE cumulative ring count, AE cumulative RA/AF value sudden increase point and the lowest point of AE b value are taken as the’ critical failure precursor point’ D. The early warning time series is: AE cumulative RA/AF value > AE cumulative ring count > AE cumulative energy > AE b value.
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Study on Crack Resistance of Prestressed RC-UHPC Composite Box Girder

LIN Shangshun, JI Bangchong, XI Zhanghua, LIN Jianfan, ZHAO Jinbing

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The prestressed RC-UHPC composite box girder with high tensile strength and corrosion-resistant ultra-high performance concrete (UHPC) as the web and bottom plate and reinforced concrete (RC) as the top plate was proposed, and a specimen was fabricated. The flexural test was carried out to analyse the crack development pattern and damage mode of the specimen; the finite element software was used to simulate the test, and the calculation accuracy of the finite element method was verified by comparing the finite element calculation results with the test data, on the basis of which 19 finite element analysis models were established to analyse the influence of various parameters on the cracking moment; relevant codes and existing literature were used to investigate the cracking moment of the prestressed RC-UHPC composite box girder. The results show that: the first crack appeared when the specimen was loaded to about 33.3 %; the cracking moment was influenced by the prestressing bar tension factor, the prestressing bar reinforcement ratio and the tensile strength of UHPC; the cracking moment calculation method based on the conversion section and the crack width calculation formulas in DBJ 43/T 325-2017 were used to calculate the cracking moment and crack width of the prestressed RC-UHPC composite box girder, respectively, and the calculated values agreed well with the test values and the finite element analysis values.
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Study on correlation between desiccation cracking and soil properties in Sanxingdui sacrifice archeology site

ZHAO Fan, YAO Xue, HU Rui, LI Junhao, LU Haizi

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Desiccation cracking is a typical deterioration in archeological excavation sites in a wet environment. To explore the correlation between the development degree of desiccation cracking and the soil properties in the Sanxingdui archeological site, the Grey Relation Analysis (GRA) is separately adopted to calculate the correlation degree between the selected six soil properties and the desiccation cracking development degree and the damage degree of fissures to the soil. This research aims to study the influence of each soil property on the development degree and to explore the feasibility of deterioration prevention and control by soil properties intervention. The result shows that the correlation degree of soil property and desiccation cracking development in descending order is as follows: the clay particle content > the clay mineral content > the plasticity index > the raw dry density > the raw moisture content, and organic content. The clay particle content, clay mineral content, and plasticity index are control indexes affecting the development of desiccation cracking, which show a positive correlation. While the raw dry density, raw moisture content, and organic content are relevant indices, in which the value of dry density is smaller, the damage degree of desiccation cracking is more serious. The soil properties intervention influences the desiccation cracking development degree to some extent, in the later practice reducing desiccation cracking by increasing dry density can be considered.
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Stability evaluation and reinforcement scheme design of dangerous rock mass in Shizhuan Mountain of Dazu Rock Carvings

Zhao Gang, Liu Dan, Jiang Siwei, Ma Runjie, Tao Zhigang, Peng Liusheng

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Due to the long-term action of natural forces, the cultural heritages of grotto temples and stone carving are extremely vulnerable to tectonic stress, crack expansion, rainwater erosion, etc., resulting in serious rock mass instability. Taking the Cliff Statues of Shizhuan Mountain in Dazu Rock Carvings as an example, through a comprehensive analysis of the engineering geological conditions of the stone carving area and the macro mechanical properties of regional rock. On this basis, the quantitative evaluation of the dangerous rock masses under the two dumping (R1) and slipping (R2) failure modes is carried out respectively, the calculation results show that the stability safety factors of R1 and R2 dangerous rock mass are 1.39 and 1.20 respectively under the influence of seismic factors. Considering the particularity of preservation status of cultural relics and the tourist visit services in the grotto area, a comprehensive treatment of "bolt reinforcement + stone masonry + crack grouting + old treatment" is adopted, which eliminates the major danger of Shizhuan Mountain cliff statues in time to ensure the safety of tourists and cultural relics. By monitoring the displacement and stress, the deformation of R1 and R2 dangerous rock masses are controlled within the range of 3 mm and 6 mm after reinforcement, which verifies the effectiveness of the reinforcement scheme. It provides a certain theoretical basis for the prevention and reinforcement of disease of dangerous rock mass in the grotto area.
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Study on prediction model of ground settlement caused by construction of double track parallel shield tunnels under arbitrary layout

wangchao, Zou Jinfeng

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In order to investigate the surface settlement pattern caused by the construction of a twin parallel shield tunnels in an arbitrary arrangement, a relevant theoretical prediction model needs to be established. Considering the effects of ground soil loss rate and convergence pattern, the classical two-dimensional Peck model is improved by introducing equivalent soil loss parameters to find the actual burial depth after tunnel convergence, taking circular tunnel as an example. Based on this, a prediction model for surface settlement due to construction of the twin parallel shield tunnels in any arrangement is established by considering three main influencing factors, such as the angle α between the tunnel axis and the horizontal plane, the radius of the two-lane tunnel (r1,r2) and the tunnel axis distance D. The applicability of the prediction model is verified by the field monitoring results and numerical simulation results of the actual project, and a prediction model for surface settlement due to construction of the twin parallel shield tunnels in any arrangement is established. The main influencing factors of surface settlement caused by construction under arbitrary arrangement of the twin parallel shield tunnels are analyzed. The results show that the prediction model of this study can be used to solve the surface settlement problem caused by the construction of a two-line parallel shield tunnel in any arrangement, and it meets the engineering accuracy requirement of 20%. The critical parameter values [α,r2/r1,D/H'] for the variation of the surface settlement curve from "V" to "W" are [60°,2.0,1.0], which can be used to make a preliminary judgment on the shape of the surface settlement curve and check the rationality of the surface settlement calculation results. It provides reliable guidance for prediction and control of surface settlement deformation in similar tunnel construction.
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Molecular dynamics simulation of corrosion of prestressed bolts in chloride ion environment

Yang Wendong, Zhang Xiang, Wang Yingnan, Jing Wenjun, Qin Hao

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In order to reveal the corrosion and failure mechanism of bolts in the complex environments at a micro level, molecular dynamics methods were introduced into the corrosion research of bolts. A molecular dynamics model was established using Materials Studio, and the molecular dynamics simulations were conducted using Lammps. The corrosion characteristics of pre-stressed bolts in chloride ion environments were simulated and studied, and the micro interaction law between chloride ion solution and the surface of bolts was explored. The results show that under the coupling effect of pre-stress and chloride ions, the iron matrix will absorb more oxygen atoms, promote the binding between oxygen atoms and iron, and accelerate the oxidation corrosion passivation of the bolts; The application of pre-stress weakens the binding of atoms inside the bolts, increasing the movement trend of iron atoms and making it easier to combine with other atoms; Chloride ions will increase the strength of the interaction between iron and oxygen atoms, promoting the binding of iron and oxygen, and chloride ions will gradually become active with the increase of prestress; With the increase of pre-stress, the movement characteristics of oxygen atoms in the solution gradually weaken because they are more likely to react with iron to form stable chemical bond. After the oxidation reaction is completed, a layer of oxide film will form on the surface of the iron substrate. In the chloride solution environment, the thickness of the oxide layer significantly increases, and the greater the pre-stress, the thicker the oxide layer.
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Study on the interfacial shear characteristics of recycled concrete aggregate and geogrid

wujianqi, luoxiang, limin, chenteng

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With the continuous development of the economy and the expansion of urban areas, it is imperative to promote the resource utilization and recycling of construction waste. As the crushed material obtained from the screening of construction waste, recycled concrete aggregate has broad application prospects. This study focuses on four different particle size ranges of recycled concrete aggregate and investigates the interface shear characteristics between recycled concrete aggregate and bi-axial polypropylene geogrid using large-scale indoor direct shear tests. The results showed that as the aperture ratio decreases, the peak shear stress and residual shear stress at the shear interface increase, and the peak shear stress occurs at a later stage. As the aperture ratio decreases, the peak apparent cohesion and residual apparent cohesion gradually increase, and the peak internal friction angle and residual internal friction angle also increase. The addition of geogrid effectively reduces the occurrence of shear dilation at the interface. By introducing the Kalhaway constitutive equation, the expression for shear stiffness is derived through linear and logarithmic fitting, and the shear stiffness corresponding to the stress state (σn,τ) is obtained. This study reveals the shear mechanism of the interface between recycled concrete aggregate and bi-axial polypropylene geogrid, and the determination of shear stiffness is of great significance in engineering for evaluating deformation mechanisms and stability.
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Field monitoring study on mechanical performance of rock bolt reinforced foundation of wind turbine

Wei Huanwei, Lei Shuli, Song Zhixin, Chen Chaowei, Hui Junmei, Song Peng, Zheng Xiao

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The load on the wind turbine during operation is complex. Therefore, based on a wind turbine foundation reinforcement project in Weihai, a system monitoring method is proposed to evaluate the performance improvement effect of the reinforced foundation in combination with the field environment. From the construction stage to the operation stage, the tower strain, welding stud strain and anchor cable axial force of the reinforced foundation are collected to study the stress response and correlation analysis of the wind turbine reinforced foundation under different working conditions, and to explore the performance improvement effect and load transfer mechanism after foundation reinforcement. The results show that the stress response of each component in the reinforcement area has trend similarity and amplitude difference, and the stress improvement effect is obvious and has great safety. The reinforcement method changes the stress boundary of the structure by outsourcing concrete and welding studs, increases the restraint stiffness of the bottom tower, redistributes the upper transfer load, shares the transfer shear force, and ensures the common deformation of the tower and concrete.The system monitoring and evaluation method based on this reinforcement scheme can effectively and timely grasp the stress state of each component of the reinforcement system and ensure the safety of the subsequent wind turbine operation. The reinforcement scheme improves the stress state of the foundation, rock bolt and flange, and the overall mechanical performance of the foundation is guaranteed, which provides a certain reference for the subsequent wind turbine foundation optimization project.
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Study on the Mechanism and Parameter Optimization of Ultrasonic Fouling Suppression in Ultraviolet Disinfection System

Chen Guang, Zhao Zhiwei, Li Li

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Ultraviolet disinfection technology has attracted more and more attention due to its advantages of no need to add chemicals, broad-spectrum disinfection, and no disinfection by-products. However, it is difficult to guarantee the disinfection effect caused by the fouling of quartz sleeves, which has become a bottleneck restricting the development of ultraviolet disinfection technology. In this study, a pilot test device was set up in the ultraviolet disinfection channel of the sewage plant, and ultrasonic waves were used to inhibit the fouling of quartz sleeves. Single factor experiments have determined that the appropriate ranges of ultrasonic power, cleaning cycle, and ultrasonic time are 500~1000W, 0.5~1.0d, and 20~40min respectively; Casing and ultrasonic both have good fouling inhibition effect. In order to further optimize the parameters, the Box-Behnken design method and the response surface analysis method were used to optimize the main factors, and the response surface regression model and the optimal solution were obtained. The results show that the optimized process parameters of ultrasonic technology for fouling inhibition and cleaning are ultrasonic power P=965.057W, cleaning cycle T=0.540d, ultrasonic time t=34.263min, and the maximum predicted relative ultraviolet intensity is 1.011. Through the statistical test, the model has a good fit, and the predicted value of the relative ultraviolet intensity obtained under the optimized process conditions is close to the experimental value, with an error of 0.89%.
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Carbon Emission Tracking Model for Construction Sites based on Earned Carbon Values

SongGuanghan, Lu Yu jie, Wang Na, Li Peixian

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The carbon emission from construction sites exhibits distinct traits of spatial concentration and temporal intensity, which underscores the pressing need for effective monitoring and regulation of its environmental impact. However, many construction site carbon assessments are carried out before or after project completion, with little attention paid to monitoring environmental performance during the construction process. This paper developed a performance assessment model called Earned Carbon Value Management (ECVM) based on construction quota theory, cyber-physical system technologies and earned value theory to assess the performance of carbon emissions during construction and to improve the accuracy and efficiency of the carbon emissions management at construction sites. ECVM, with three key parameters and four key indicators, can link the construction carbon emission with the project completion and resource consumption and has. The model has been demonstrated in a construction project in Shanghai. The results show that the model is able to analyze the relationship between construction progress and carbon emissions during the construction process and analyze the causes of deviations and propose targeted corrective measures based on carbon emission performance indicators. The model presented in this paper is generic and can be used for any construction projects that aim to reduce carbon emissions.
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Data Quality Evaluation for Dynamic Response Monitoring of Bridge Cables

dengyang, zhangqiang, zhongguoqiang, liushang, xurun, juhanwen

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There was a large amount of low-quality data in the monitoring data of bridge cable dynamic response. The existing data detection research focused on obviously abnormal data with abnormal time-domain waveforms. However, there was chaotic data in frequency-domain characteristics with normal time-domain waveforms in the monitoring data, which can’t accurately obtain the dynamic characteristics of bridge cables. Aiming at this problem, the existing abnormal data detection was extended to data quality evaluation, and the obvious abnormal data and frequency-domain chaotic data were detected at the same time. The data quality evaluation method of bridge cable dynamic response monitoring was established by using a convolutional neural network (CNN) and data frequency-domain features. The implementation process included: the time-domain data sequence was transformed into a power spectral density function (PSDF) by fast Fourier transform (FFT), the Gramm angular field (GAF) method was used to visualize the PSDF sequence, and a CNN model was designed and built to evaluate the data quality automatically. Taking the cable acceleration monitoring data of a cable-stayed bridge as an example, the applied research was carried out. The results show that compared with the time-domain sequence detection method, the PSDF sequence detection method can better distinguish normal and pseudo-normal data, and has a higher evaluation accuracy rate; The accuracy rate of the CNN model established by using the monitoring data of two sensors to evaluate the quality of all 26 sensor monitoring data is above 94%; In addition, the evaluation model established by this method is applied to the monitoring data quality evaluation of another similar bridge with an accuracy of 95%.
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Effect of Manufactured Sand Dosage on Flexural Performance ofSelf-Compacting Lightweight Aggregate Concrete Beams

ZHANG Shuyun, LIU Jianbo, YANG Xulong, LI Qiang, BAI Miaomiao

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To explore the influence of manufactured sand dosage on the flexural performance of self-compacting lightweight aggregate concrete beams(SCLC), five SCLC with 0%, 30%, 60%, 80% and 100% manufactured sand dosage were designed and fabricated for four-point bending test. The deflection curve, mid-span deflection and crack distribution of SCLC beams with different manufactured sand dosage under load were studied, and the influence of manufactured sand dosage on its cracking moment and flexural capacity was explored. The results show that the average strain of each test beam section conforms to the plane section assumption, and the load-deflection curves are basically similar. With the increase of manufactured sand dosage, the SCLC beam has more secondary cracks and more uniform crack distribution. The maximum crack width decreases under the same load before yielding. The mid-span deflection and ultimate bearing capacity reach the maximum when the manufactured sand dosage was 80%, which were increased by 16.13% and 6.62% respectively compared with SCLC beams. Using the deflection calculation formula of lightweight aggregate concrete, the deflection calculation value of each test beam is different from the test value. The cracking moment of the test beam is calculated by the standard formula, and the calculated value is quite different from the test value. Through the analysis of test results and calculation of flexural bearing capacity, the optimal dosage of manufactured sand in SCLC is 60%~80%.
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Modeling method of floating column foot node based on multi-spring model

Zhan Xin, Qiu Hongxin, Lu Weijie

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Floating shelf is a typical structural form of column base in traditional wood structure, and wood column is prone to swing under horizontal load. The rocking behavior of timber columns shows that the floating column base joints have semi-rigid characteristics, which plays an important role in resisting lateral load and maintaining overall stability of timber structures. In this paper, a modeling method of rocking wood column base joints is proposed. A row of axial springs are arranged at the column base to simulate the stress state of the contact interface between the column bottom and the foundation stone. The corresponding numerical model is established based on the OpenSees platform. The validity of the modeling method is verified by comparing with the refined finite element model and the experimental data in a large number of related literatures. At the same time, some factors affecting the modeling method are analyzed, including the contact stiffness, distribution mode, spring number and material constitutive of the column spring. The results show that the modeling method is relatively insensitive to the contact stiffness. It is suggested that the effective compression depth of the timber column is the radius of the timber column to determine the contact stiffness of each spring element. The three distribution modes are applicable to the modeling method, and the number of spring units should be no less than 10. For wood columns with high axial compression ratio, the ElasticPP material constitutive considering the spring element entering plasticity should be adopted in the modeling process.
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Theoretical evidence of closure alignment control based on bearing forced displacement method for a steel girder bridge

ZhaoZhihang, ZhouShijun, ZhouCao, ChenZengshun, HeYingying

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The bearing forced displacement method is a widely used control method in the closure construction of steel girder bridges. However, the theoretical research on the construction process of the bearing forced displacement method still needs to be completed. In this paper, based on the differential equation of Euler beam deflection, the integral method is used to solve the flexural closure solution of a three-span continuous girder in two conditions, namely, the bridge completion and closure in stages and the one-time bridge completion. The beam deflection functions obtained in both conditions are identical, which proves that the ideal one-time bridge formation can be achieved by applying the bearing forced displacement method. Finally, with a closure construction application of a three-span continuous steel truss bridge, the applicability of the forced displacement method in bridge alignment control applications is verified. The theoretical proof can provide a theoretical basis and technical reference for the engineering application and promotion of the bearing forced displacement method.
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Experimental Study of electro-osmotic interface resistance based on Electrochemical Reaction

Hu Hao, GAN Qiyun, ZHOU Jian, MA Yuchun, JIANG Yicheng, ZHU Zeming

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In order to the issue of high energy consumption and significant potential loss at the soil-electrode interface during electroosmotic consolidation, this study investigates the impact of electrode reactions on interface resistance from an electrochemical perspective. By using a self-designed one-dimensional electro-osmotic consolidation device, indoor experimental studies were conducted to explore the trend of the clay-electrode interface resistance under different electrode materials and different power supply modes, and the mechanism was elucidated using an electrochemical interface resistance model. The experimental results show that electrode reactions alter the interface electrochemical properties, affecting interface resistance and thus the electroosmotic drainage rate. The anode interface resistance is significantly affected by electrode reactions, with a smaller anode interface resistance observed in the EKG electrode under long-term electrification, while the metal electrode exhibits a larger anode interface resistance due to the combined effects of concentration polarization and surface membrane resistance. Using an optimized power supply strategy can help alleviate interface polarization and inhibit interface resistance growth.
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Study on the Stability of Suspended Anchor Bolt Reinforcement Project of Dazu Rock Carvings Beishan Grottoes

Feng taibin, liu keyuan, lei xiaotian, jiang siwei, Chen huili, Zhang bingfeng, Ma runjie, Tao zhigang

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Under the influence of years of weathering and self weight stress, a large number of cracks have appeared in the cave wall and its roof of Cave 168, Beishan, Dazu Rock Carvings, resulting in the instability of the surrounding rock at the top of the cave and the danger of instability and collapse. In order to effectively reinforce the broken surrounding rock of the roof of the flat roof grottoes, this paper adopts a roof reinforcement method of hanging anchor bolts according to the geological conditions of the site. Firstly, based on on-site investigation, the distribution pattern of cracks in the roof slab was determined, and the main causes of cracking in the cave roof were summarized. Then, the anchoring length of the anchor rod was calculated using the idea of the New Austrian Method considering the most unfavorable stress on the surrounding rock. Finally, numerical simulation was used to analyze the displacement and stress changes of the cave roof under rainfall conditions using the suspension beam reinforcement method. The results showed that: under the conditions of suspension anchor rod reinforcement, The displacement of its top plate in all directions shall not exceed 1mm; The stress at the cave entrance and inside the cave is relatively concentrated, with the maximum tensile stress being less than the tensile strength value of sandstone, and the surrounding rock of the roof is in a stable state; During the suspension anchor rod support process, the anchoring section mainly bears tensile stress, with an average tensile stress of 4.3MPa, indicating a good stress situation. From the curve data before and after on-site reinforcement, it can be seen that the suspension beam reinforcement method has reduced the fluctuation value of cracks. It can be considered that the grotto maintains a stable state under the conditions of suspension anchor rod reinforcement. This suspension anchor rod reinforcement method provides a reference for the stability support of thin and broken roof slabs similar to flat roof grottoes.
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Reliability analysis of damaged concrete beams based on the rust crack width

baiyuliang, jinweiliang

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By introducing the fatigue damage factor and the creep damage factor, the calculation model of the corrosion depth of the steel bar after the corrosion cracking of the protective layer of the concrete beam with fatigue and creep damage was established. According to the durability design standard of concrete structure, the durability limit state equation controlled by the rust crack width was established. The Monte-Carlo numerical simulation method was used to calculate the reliability of six concrete test beams within the crack width limit. The sensitivity of the four parameters including corrosion current density, concrete compressive strength, protective layer thickness and steel bar diameter was calculated by using the checking point method. The research results show that the reliability will drop from 0.9 to 0.1 with the increase of the corrosion time and the increase of the holding time for 3 months has little effect on the reliability of the beam after the cyclic loading of 60% of the fatigue life times. The increase of the protective layer thickness and the decrease of the diameter of the steel bar can both improve the reliability of the beam and slow down the decline rate of the structural reliability in the early stage of the corrosion of the steel bar. The steel bar diameter of 9 mm can be used as a reference value for the durability design of damaged concrete beams. The sensitivity of the three parameters of corrosion current density, protective layer thickness and steel bar diameter is so relatively large that three parameters are the main influencing factors of durability limit state reliability.
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Research on calculation method of deep foundation pit water injection and underwater excavation design

ZOU Zhiyan, LIU Shenglin, ZHANG Yibo, FU Xudong

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Water injection and underwater excavation is a new method of foundation excavation. It is used to solve the problem that traditional methods of off-pit precipitation and in-pit drainage cannot be implemented when there is a stable connection between groundwater in the foundation pit and river water. The design calculation method of deep foundation pit injection and underwater excavation is proposed. Combined with the deep foundation pit project of steel sheet pile cofferdam, a water injection and underwater excavation scheme was developed, and a corresponding numerical model was established to study the force and deformation law of the support structure corresponding to the deep foundation pit firstly precipitated to form dryland working conditions for excavation, then injected water for underwater excavation, and then precipitated after underwater pouring of sealing concrete. The water injection height has also been optimized. The conclusions are as follows: First precipitation to form dryland working conditions when the maximum depth of precipitation depends on the stability of the soil at the bottom of the pit against flowing sand and pipe surges. When the excavation depth increases from 2m to 7m, horizontal displacement of support structure increased by 53.6%, the maximum value of plastic uplift at the bottom of the pit gradually increases to 59.0mm. When re-injecting water for underwater excavation, increasing the height of water injection can effectively reduce the uplift deformation of the soil at the bottom of the pit and the horizontal displacement of the support pile, the critical height of water injection is 9m. When the water injection height exceeds the critical value, the effect of inhibiting the deformation of pit bottom and support piles will be weakened. The thickness of the sealing concrete depends on its floating stability and strength. The embedded depth of steel sheet piles depends on the overall stability of the support structure under the precipitation conditions after the concrete is placed underwater. The research results are of reference value for the design and construction of similar deep foundation pits.
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Experimental study on influence of bolt arrangement on bending behavior of steel-wood composite beam

wuzhenzhen, Tangshenghua, wangjiejun, liuruiyue

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In order to promote the application of bolt fasteners with diameters of up to 10 mm in steel-wood composite structures, the effects of the number of transverse rows of bolts, bolt diameters and longitudinal spacing of bolts on the bending performance of steel-wood composite beams were investigated. By designing a composite beam with a I-steel beam at the lower part and wooden board at the upper part, the upper and lower parts connected by bolts. a three-point bending load test was carried out on 8 test beams, to observe the failure mode, mid-span deflection variation, mid-span section strain and slip effect at the steel-wood intersection at the end of the beam respectively, to investigate the effect of different bolt parameters on the flexural mechanical properties of the steel-wood composite beam. The test results showed that the main damage mode of the steel-wood combination beam is the mid-span deflection up to 1/27 of the calculated span,resulting in deformation damage; Composite beams had high flexural capacity and ductility coefficient. The maximum relative slip at the steel-wood interface of each specimen was 2mm~6mm; Among the parameters of bolt arrangement, the longitudinal spacing of bolts had greater influence on the strain difference at the steel-wood interface in the span of the composite beam, while the bolt diameter had less influence. The concept of bolt area ratio of steel-wood composite beam was proposed, i.e. the ratio of total bolt area to compressive area of wood board. With the increase of the bolt area ratio, the flexural load capacity of the specimen increases significantly and the maximum slip at the intersection decreases gradually, although the displacement ductility coefficient decreases. The range of bolt usage can be quickly calculated by optimum the reasonable range of bolt area ratio, which provides design reference for practical application of such steel-wood composite beam.
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Experimental study on rapid disposal of high moisture content mud by CaCl2-APAM-PAC of composite flocculant

Ma Yingjian, Fang Zhou, Cheng Huifeng, Su Bin, Liang Dengqin, Qin Xinhao, He Bin

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In engineering construction, waste mud often contains an extremely high water content that can significantly impact the environment. Addressing the issue of dehydration is therefore a primary concern. To address the problem of high water content mud water separation, this study selected three types of flocculants CaCl2、anionic polyacrylamide(APAM） and Poly aluminum Chloride(PAC) ,and then designed a 3-factor and 4-level orthogonal experiment using the comprehensive balance method. Indicators such as the 48-hour dehydration amount and pH value of the supernatant were selected, and range analysis and variance analysis were conducted to find the optimal combination of composite flocculants. The flocculation mechanism was also discussed through orthogonal test results and SEM microanalysis . The experimental results showed that dividing the dehydration rate curve over time into high, medium, and low dehydration zones, as well as fast and slow dehydration stages, led to a decrease in the overall mud dehydration rate. However, the high dehydration zone group had a higher dehydration rate at 12 hours, which met the requirements for fast dehydration. Additionally, the three flocculants showed a certain synergistic effect. Through range analysis and variance analysis of orthogonal tests, the optimal combination of composite flocculants was found to be 0.25% CaCl2 + 0.12% APAM + 0.17% PAC of the total mud mass. Based on mechanism analysis, the flocculation process of composite flocculants was divided into five stages: charge neutralization stage, bridging stage, adsorption agglomeration stage, network sedimentation stage, and solidification enhancement stage.
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Study on the section-classification-based steel plate width-thickness ratio of Steel-Concrete Composite Beam with U-section

CHENG Rui, YU Yuanlin, ZHANG Jiayu, ZHNAG Qingfeng

Abstract: (60) HTML (0) PDF (0.00 ByteKB) (0)

In order to study the plate width-thickness ratio limits of steel palte based on section classification for Steel-Concrete Composite Beam with U-section (SCBU), monotonic static loading tests were conducted on five SCBU specimens. The damage modes, load-displacement curves and plastic deformation capacities of SCBU with different combinations of height-thickness ratios of outer steel-encased web in compression area and width-thickness ratios of compressed flange were analyzed. The test results show that the width-thickness ratio of the steel plate has a direct influence on the buckling deformation and plastic deformation capacity of the SCBU. All the specimens suffered local buckling before reaching the peak bearing capacity, the failure mode was bending plastic damage. Meanwhile, the finite element analysis results show that the nonlinear behavior between the steel plate web and compressed flange interacts with each other, the buckling moment of the plate advances with the increase of width-thickness ratio of the adjacent plate, and the degree of plastic development of the SCBU decreases with the increase of width-thickness ratio of steel plate. Based on the results of the test and finite element parametric analysis, the recommended limit value of width-thickness ratio for class II section (Class 2) steel palte of SCBU is proposed and compared with the code limit values.
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Predicting the CO2 adsorption capacity of porous biochar based on machine learning

CHEN Yifei, ZHANG Xiaoqing, TAN Kanghao, WANGJUNSONG, QIN Yinghong

Abstract: (306) HTML (0) PDF (0.00 ByteKB) (0)

Porous biochar contains rich multi-scale pore structure, which makes it have excellent CO2 adsorption performance. To address the shortcomings of the traditional CO2 adsorption prediction models built with experimental data, such as low accuracy and complicated calculation, this paper adopts machine learning methods such as gradient boosting decision tree (GBDT), extreme gradient enhancement algorithm (XGB), and light gradient booster algorithm (LGBM) to make model predictions of CO2 adsorption by biochar, and conducts a comparative analysis of the prediction results. The results showed that the top three factors affecting CO2 adsorption were the specific surface area, C content, and O content of biochar in order. all three algorithms could effectively predict the CO2 adsorption performance of biochar. In comparison, LGBM has the highest prediction accuracy of 94%; GBDT has significant advantages for anomalous sample data processing; and XGB has more stable prediction results for different test set variations. The results of this model can provide important references for regulating and optimizing the composition and structure of biochar.
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Gravity-well friction pendulum bearing and its seismic performance

Cao Sasa, Zhang Feitao, Zhang Liwen

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The traditional bridge with isolation bearings has the issue of residual displacement of the isolator and the response of internal pier force during the impact of an enormous earthquake or near-fault earthquake. This research suggests a variable-stiffness friction pendulum bearing based on a gravity-well surface, gaining inspiration from the facility for gravity-well surfaces in the Science Museum. Its surface is made up of a gravity-well surface outside and a sphere inside. First, the theoretical derivation-based restoring force model in the horizontal shear direction is revealed. Second, a footprint variable stiffness friction pendulum bearing specimen is designed, constructed, and put through a cyclic shear test to further examine its mechanical and hysteresis characteristics. The friction material was a modified ultra-high molecular weight polyethylene with better compression resistance. In the end, numerical simulations were used to compare the dynamic properties of the gravity well friction pendulum bearing with the spherical bearing. The sliding surface of the variable stiffness double friction pendulum bearing is asymmetrical. The high local stress on the friction pad can be accommodated by the modified ultra-high molecular weight polyethylene (UHMWPE) friction material. The gravity-well friction pendulum bearing can also significantly reduce the internal force demand under the action of ground motion when compared to the conventional spherical double friction pendulum bearing, and it has the same superior self-reset performance as the spherical friction pendulum bearing small radius.
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The influence of fiber content on the macro and micro characteristics of reinforced soil

chen zhibo, guo xuewen, dai menglan, lai hanjiang, xie yongning

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Fiber content is an important parameter affecting reinforced soil. In existing research, the range of fiber content values is generally small, and the physical and mechanical properties of reinforced soil with higher fiber content are not well understood. Therefore, in order to study the impact of higher fiber content on rice straw fiber-reinforced soil, this paper sets up 10 fiber mass fractions and uses direct shear tests for research, exploring the effect of different fiber contents on the strength characteristics of reinforced soil. Additionally, scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) tests are used to analyze the microstructure features of fiber-reinforced soil. The results show that adding fibers can effectively improve the shear strength of the soil. The reinforcement mechanism of fiber-reinforced soil is related to fiber content. A small fiber content has little effect on the porosity of the soil, and the reinforced soil is based on the soil skeleton. When the fiber content is high, the porosity increases significantly, and the main structure of the reinforced soil will be composed of both the soil skeleton and the fiber skeleton.. The research results of this paper can provide a reference for the design and construction of fiber in practical engineering applications such as foundation treatment and slope protection.
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Study on fatigue life prediction and interface slip zone quantitation of corroded PC beams

DAI Lizhao, LIU Jingjin, WANG Lei

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The combined effects of repeated load and corrosion can cause fatigue damage of prestressed concrete (PC) beams, which would reduce its service life. The fatigue crack growth size of strand and ?cumulative residual strain of concrete were taken as damage parameters in the present study, a quantitative method of uncoordinated deformation in bond-slip zone considering the residual strain of strands and steel bars and a fatigue life prediction method of corroded PC beams were proposed. The methods comprehensively consider the influence of fatigue crack growth of steel strand, interface corrosion fatigue bond degradation and fatigue damage of concrete. Then the rationality of the fatigue life prediction method was verified by experimental data, and the interfacial fatigue bond-slip of corroded PC beams under different prestress, corrosion degree and stress level were discussed. Results show that the proposed methods can effectively predict the interface slip and the fatigue life of corroded PC beams. The prestress is an important parameter that affects the fatigue bond-slip of corroded PC beams. With the increase of corrosion loss and stress level, the specimen is prone to occur the fatigue bond-slip, and the increase of prestress force can effectively reduce the interfacial fatigue bond-slip. At the high stress levels, the more serious strain incompatibility will lead to more residual slip, the slip curve and its slope would rise and steepen as the stress level increases.
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Experimental study on hysteretic behavior of a new two-stage buckling-restrained brace

Yuan Tao, Sun Tongfei, Liu Ye, Dai Kaoshan, Zhu Zheming

Abstract: (68) HTML (0) PDF (0.00 ByteKB) (0)

A novel two-stage buckling-restrained brace (TS-BRB) has been proposed to enhance the performance of conventional buckling-restrained braces (BRB), particularly addressing the problem that conventional BRB cannot provide lateral resistance and energy dissipation capacity to the structure after failure under the action of major-after shocks. The energy dissipation unit of TS-BRB consists of three Q235 steel plates in series with tapering cross-section along the longitudinal axis. The energy dissipation section in the middle plays the role of energy dissipation firstly during earthquake, and if this section breaks, the limit slot in the restraint unit ensures the rest of the energy dissipation section keeps working, thus giving TS-BRB a higher energy dissipation capacity than conventional BRB. The slipping distance of TS-BRB is limited by varying the length of the limit slot, enabling the brace to meet the requirements for structural damping design. Test results demonstrate that the hysteresis curve of the TS-BRB is saturated and the shape of the hysteresis curve is consistent with theoretical expectations. TS-BRB exhibits evident two-stage energy dissipation characteristics, with the end energy dissipation section continuing to operate after the middle energy dissipation section breaks. The additional accumulated energy dissipation after the fracture is 138.41% of that before the fracture. The TS-BRB provides a solution to the issue of conventional BRBs losing load-bearing and energy-dissipation capacity immediately after fracture and offers greater energy dissipation reserves for the structure. Finally，a numerical model was established in ABAQUS，which demonstrates that the hysteretic curve of numerical simulation agrees well with that of experiment．
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Study on time-dependent interfacial stress of FRP-strengthened RC beam

Yao Weilai, Liu Yuanxue, Sun Tao, Mu Rui, Yan Renzhang

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Based on the massive applications of FRP-reinforced structure technology, the time-varying patterns of interfacial stresses of FRP-strengthened RC beam under sustained load are investigated in this study. A finite element (FE) model was developed to analyze the external FRP strains, and the correctness and usability of the FE method were verified by comparing the predicted results with the test results. For the FRP end area, FE method and analytical method were applied to conduct investigations considering the spew fillet of adhesive and the secondary loading of the reinforced structures. For area near the intermediate concrete crack, the analytical method was used to conduct calculations. The results show that the concrete creep leads to the increase of interfacial stresses with time, and the adhesive creep leads to the relief of stresses. This conclusion is applicable to both areas mentioned above and is not affected by the spew fillet of the adhesive and the secondary loading of the reinforced structures. In the FRP end region, the FE results and the analytical results are in good agreement.
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Study on the dynamic behavior and energy evolution at rockburst mutation moment based on DEM

WEI Rui, zhaocheng, QIAN Yuan

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The dynamic behavior and energy evolution of rockburst at the moment of sudden instability are the key to reveal rockburst formation mechanism. Based on the instability theory and stiffness theory, a combination model consists of rockburst body and its surrounding rock was established using the three-dimension discrete element method (DEM). With it the energy evolution process of the system is visualized through secondary development and the ejection phenomenon of rockburst is simulated successfully. Based on the numerical simulation, the time sequence characteristics and energy evolution laws of instability of the system are studied. The results show that the rockburst rock body reaches the peak stress slightly earlier than the surrounding rock body. The rupture and softening of the rockburst body after the peak stress results in the unloading of the surrounding rock body, and causes its stress changes from increase to decreases. The surrounding rock mass then has a rapid rebound deformation to the rockburst body, and the elastic energy stored in the surrounding rock body converges to the rockburst body. In this process, the positive feedback regulation mechanism formed by the interaction of the two subsystems accelerates the fracture processes and finally leads to dynamic instability. The research results can provide theoretical reference and technical support for further revealing the rockburst mechanism.
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Cyclic Shear Characteristics of Granite Residual Soil-geogrid Interface with Different Water Content

Zhou Weidong, CHEN Shuqi, Liu Feiyu, LIU Hongbo

Abstract: (86) HTML (0) PDF (0.00 ByteKB) (0)

Water content has a great influence on the mechanical properties of granite residual soil reinforced with geogrids. In order to study the cyclic shear characteristics of granite residual soil-geogrid interface under different water content, a series of cyclic shear tests were carried out by large indoor direct shear apparatus. The shear stress-shear displacement curves, shear strength, shear stiffness and volume of the soil-reinforced interface were analyzed under four kinds of water content (13%, 19%, 25%, 32%), three kinds of normal stress (50, 100, 150kPa), four kinds of shear frequency (0.2, 0.5, 1, 2Hz) and four kinds of shear amplitude (5, 10, 15, 20mm). The test results show that: When the soil is saturated with water content of 32%, the peak shear stress and shear stiffness of the interface increase first and then decrease during the cyclic shearing process. The initial increase of the peak shear stress under the normal stress of 50, 100 and 150kPa is 6.2%, 22.3% and 33.0%, respectively, indicating that the increase of the normal stress is greater than that of the interface at the initial stage. Under unsaturated water content, the interface of soil-reinforced soil shows shear softening characteristics. When the normal stress is 50kPa, the shear strength of the interface reaches the peak value when the water content is 25%. When the normal stress is 100kPa and 150kPa, the cyclic shear strength of the interface is negatively correlated with the water content, decreasing by 35.47% and 43.17%. When the water content is 13%, 19%, 25% and 32%, the final shear shrinkage of the interface is 4.6, 7.7, 8.6 and 7.2mm, respectively, indicating that the shear shrinkage increases first and then decreases with the increase of water content. At each water content, the maximum shear stiffness of the interface decreases first and then increases with the increase of shear frequency, and decreases with the increase of shear amplitude. The shear frequency of 0.5Hz has the strongest weakening effect on the interface shear stiffness of the interface.
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Study on Dynamic Factors of the Guideway Beam of Low and Medium Speed Maglev Vehicle-Bridge System based on reliability theory

wang li dong

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Affected by the randomness of track irregularity, the dynamic factor of the guideway beam caused by the maglev vehicle has obvious uncertainty. In order to accurately calculate the reliability of dynamic factors of the guideway beam, a vertical coupling vibration model of the medium and low speed maglev train-bridge system was established, which was composed of the maglev vehicle, the simply supported girder and the suspension control system. Then, combined with the idea of orthogonal random function and the strategy of selecting points via number theoretic method, the reduced dimension simulation method of track irregularity was developed, by which only two random variables were needed to simulate the representative samples of the track irregularity. Finally, based on the probability density evolution method and the equivalent extreme-value principle, a reliability evaluation method for the guideway beam was proposed, by which the probability density function, cumulative distribution function of the dynamic system and the dynamic reliability of the guideway beam can be accurately obtain. The Changsha low-medium speed maglev line, as a case study, was numerically analyzed. The reliability of the calculation model was verified by comparing with the results of field measurement and Monte Carlo method. Furthermore, the effects of vehicle speed, vehicle weight and track irregularity roughness on the dynamic factors and reliability of the guideway beam were discussed. The results indicate that the reliability of the guideway beam is 1 within the speed range of 60 to 140 km/h. However, since the dominant frequency of the vehicle load is approaching to the basic frequency of the vertical vibration of the guideway beam at the speed of 80 km/h, which makes the value and dispersion of the dynamic factors at this speed the largest. The dynamic factors of the guideway decrease as the weight of vehicle increases. In addition, the track irregularity roughness has a significant impact on the dynamic factors of the guideway beam. If the reliability of the guideway beam is required to be 1, the track irregularity amplitude should be controlled within 5.03 mm.
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Shear mechanism and shear strength calculation of composite shear connectors under biaxial load

马亚飞, Hu Tao, Zhang Bachao, zhou biao, wang lei, zhang jianren

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To investigate the shear performance of composite shear connectors under biaxial load, a finite element model was established and verified by experimental tests. The failure modes of composite shear connectors under biaxial load and unidirectional push-out load were compared, and the relationship between biaxial load and shear strength ratio was also analyzed. The effects of concrete strength and through reinforcement diameter on the shear strength under biaxial load were clarified. The shear mechanism of composite shear connector was revealed. A shear strength model of composite shear connector under biaxial load was established by multivariable regression analysis. The results show that lateral pression can effectively prevent the transverse expansion of concrete, and a longitudinal main crack and a few transverse microcracks appears in the concrete slab. Under the action of unidirectional push-out load, the composite shear connector fails due to the penetration of splitting cracks in the concrete slab. Lateral pression increases the shear strength of composite shear connectors, but the biaxial load effect is small when the concrete strength is high and the diameter of through reinforcement is large (shear strength ratio is 1.05). The shear strength of composite shear connector significantly increases with the increase of concrete strength and through reinforcement diameter under biaxial loading.
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Effect of electric curing on mortar forming temperature and early strength under negative temperature environment

YANG Zhouzhou, MAO Jianghong, LI Bixiong, QIAN Wei, LI Lisi

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In order to study the effect of electric curing on the early strength development of mortar mixed with calcium formate early strength agent under a negative temperature environment, calcium formate early strength agent with 2% mass of cementitious material was mixed into the mortar, and electric curing was carried out by passing alternating current in a -10°C environment. During the test, the real-time changes of the mortar internal temperature under different energization parameters were monitored by a thermometer, and finally, the strength of the mortar energized for 1 day and the strength of subsequent standard curing for 3 days and 7 days under different energization parameters were tested. The test results show that the addition of calcium formate to the mortar can effectively reduce the resistance and thus improve the energizing efficiency, and the initial resistance of the mortar specimens with calcium formate is 1/4 that of the mortar without calcium formate, so that it can achieve a good heating effect at a lower applied voltage. Calcium formate also has an obvious early strength effect after 1 day of electric curing, which can promote the early strength development of the mortar. The strengths at 3 days and 7 days of the calcium formate-doped mortar increased by 59% and 29%, respectively, compared with the un-doped calcium formate mortar under the same energizing parameters.
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Study on ultrasonic monitoring of coagulation process of geopolymer mortar

Long Shiguo, Chen Jinjie, LI Rijin, Zhou Jinyi, Xu Jitong

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Geopolymer is a kind of green and low carbon cementing material, and the study of the cementation process of geopolymer is essential for engineering application. In order to investigate the mechanism of geopolymer cementation, five groups of geopolymer mortars with different mixture proportion (slag: fly ash) were placed in a special device and monitored them in real time by three ultrasonic inspection methods. The initial and final setting time of the geopolymer mortar were characterized by energy reception ratios and verified with the results of the penetration resistance method. The results demonstrated that the setting rate of geopolymer mortar slows down with the decrease of mixture proportion. The ultrasonic transmission method could realized the whole monitoring of mortar. The mean error of initial setting time and final setting time of ultrasonic transmission method was 7.9% and 6.6% respectively. The reflection method has high accuracy in determining the initial setting time of mortar, and its mean error was 2.8%. The ultrasonic guide wave method could realized the whole monitoring of mortar. The mean error of initial setting time and final setting time of ultrasonic transmission method was 3.3% and 2.5% respectively. Among the three methods, ultrasonic guided wave method is more suitable for monitoring the coagulation process of geopolymer mortar.
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Analysis of effect of liquefaction interlayer on isolation response of shallow foundation structures

hujilei, shenwenxaing, yangbin

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A Liquefaction of sand interlayer will not only cause failure of the foundation, but also play a role in absorbing the shock of the superstructure, while the overburden can reduce the settlement of the building but amplify the earthquake effect. Therefore, it is necessary to consider the coupling effect of liquefaction interlayer and overburden on the isolation of the building under the interaction between structure and soil. finite element and finite difference coupling dynamic analysis methods are used to analyze the effects of different seismic intensity, sand density Dr And liquefaction layer thickness to depth ratio K (considering the coupling effect of liquefaction interlayer and overburden) on the isolation of superstructure. The results show that the structural acceleration spectrum ratio decreases first and then becomes stable with the increase of vibration intensity. When the vibration intensity exceeds a certain threshold, the isolation effect of the liquefied layer does not increase. loose sand (Dr=30 %) the isolation effect is better than that of medium-density sand (Dr=50 %) and dense sand (Dr=70 %), but it will cause non-negligible settlement hazards. In a short period, it will act as a seismic force. Combined with
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Current status and prospects of research on conductive concrete in cold regions

LU Jianguo, YANG Xinlian, PU Wanli, WAN Xusheng, WANG Yindong, TAN Liling

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Snow and ice on roads, bridges and reservoir dam panels in cold regions seriously affect the performance of the project, and have a significant impact on the safe operation and maintenance of the project. The extensive use of de-icing materials, e.g., de-icing salt and snow melting agents, lead to serious environment pollution. Conductive concrete, as an environmentally friendly and efficient snow/ice melting technology, plays an important role in ensuring the safe operation and maintenance of engineering, extending the service life of the project, and improving the service quality of engineering. At the same time, the use of conductive concrete as building materials in cold areas has indoor heating function, which can alleviate the energy shortage to some extent. This paper reviews the preparation process of commonly-used conductive concrete, analyses the mechanical-electrical-thermal properties of some kinds of conductive concrete, e.g., carbonaceous conductive concrete, metallic conductive concrete and complex-phase conductive concrete, and then researches the influence of conductive materials on the mechanical performance of conductive concrete (e.g., conductivity, frost resistance, and durability). Based on analysis above, the research concepts of conductive concrete in cold regions are proposed considering the goals of high performance and low cost: 1) Recycling materials, such as recycled carbon fiber, should be widely used to develop multiphase conductive concrete; 2) Magnetic separation fly ash, slag, and silica fume are extensively used as admixtures in conductive concrete; 3) Investigating the heating and conductivity performances of conductive concrete under the low charging voltage; 4) Utilizing comprehensive clean energy (e.g., solar energy, wind energy, etc.) to generate electricity for conductive concrete; 5) Exploring the conductive concrete-geotechnical-environment feedback mechanism under complicated engineering environment. This study is aimed to provide guidance for the prevention and control of engineering disasters and indoor heating of buildings in cold regions.
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Study on fatigue crack life cycle growth characteristics of steel bridge deck

lunaiwei, cuijian, luoyuan, wanghonghao

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The initial welding defect is the key factor that affects the fatigue performance of the structural details of the orthotropic steel bridge deck. In order to study the whole life cycle dynamic characteristics of crack initiation and propagation of the joint weld between the top plate and the longitudinal rib of the orthotropic steel bridge deck, based on the fracture mechanics theory and ABAQUS-FRANC3D interactive technology, the dynamic characteristics of the stress intensity factor in the whole process from the weld buried defect to the fatigue fracture were studied, the crack shape development law was revealed, and the influence of sensitive parameters on the crack growth rate and fatigue life was analyzed, The full life propagation behavior of fatigue crack is clarified, and the reliability of the research results is verified by the full scale segment fatigue test of steel bridge deck. The analysis results show that the fatigue crack growth behavior of steel bridge deck can be divided into three stages: burial stage, initiation stage, and propagation stage. The distribution of stress intensity factors in the buried initiation stage and the propagation stage along different crack paths is exactly opposite; Buried cracks of any initial shape tend to be round with continuous expansion, and surface cracks of any shape gradually flatten, which reasonably explains the flat shape of surface cracks when they continue to extend to the roof; The crack propagation rate along the upper surface of the buried stage is 54% higher than that on the lower surface. The crack propagation rate from the buried initiation stage to the roof direction is larger; The crack shape ratio a/c and buried depth have a great influence on the initiation life, and the initiation life accounts for the majority of the total fatigue life.
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Study of shear slip zone in direct shear test of granular materials based on photoelastic method

Hu Wen Tao, Xiao Jin, Yin Jiang Hao, Geng Da Xin, Xu Chang Jie, Li Shun Wen, Wu Wen Bing

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The development pattern and distribution characteristics of the shear zone of the particle direct shear test determine the strength of the particle body, but it is not easy to observe. The direct shear test of transparent polycarbonate particles was carried out using a homemade test device. Based on the principle of photoelastic method, the development process of force chain, the development law of main contact angle and the development law of shear slip surface of particles were studied by observing the shear mechanical properties, stress chain distribution and displacement field of particles, and the simulation analysis was carried out in PFC2D discrete element software. The tests show that: the stress shielding phenomenon exists in the force chain distribution of the particle system during the direct shear process; the strong force chain, contact angle and main stress direction of the particle system are deflected, and the deflection characteristics are basically the same; the particles form an arch-shaped shear slip surface during the shear process, and form an arch-shaped slip shear zone together with the horizontal shear surface. The arch slip zone forms at the beginning of shear and continues throughout the shear process. At peak shear stress, the height of the arch-slip zone is proportional to the initial normal force and is between (13~15) d50 thick. The arch slip zone gradually decreases during the residual stress phase, and the arch slip zone gradually tends to a steady state, and the height of the arch slip zone under different initial normal forces does not differ significantly during the residual stress phase,and thickness between (8~9) d50.
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Study on pseudo-static test of slope- single load rock-socketed pile system under horizontal load

LIU Liping, LI Meng, ZENG Weiming, LI Ruifeng, LIU Lei

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In order to study the bearing characteristics of single loaded rock-socketed pile under horizontal load, In view of the difficulty and complexity of dynamic test, adopt pseudo-static test, rock and pile are simulated with similar material, considering the vertical and horizontal load, designed and completed three groups of model test. The elastic bending moment, rock pressure around the pile and the hysteresis curve of the pile top are analyzed under different slope and elastic modulus of rock. The results show that the horizontal bearing capacity of pile foundation of rock slope is mainly related to shallow slope within the range of buried depth above 3D (D is pile diameter) . The failure pattern of the downslope rock mass is similar to that of the soil slope, which goes through three stages: the emergence of cracks, the development of failure surface and the failure of the shallow slope body, but the upslope rock mass has not formed a complete failure surface. Finally, the shear failure of pile foundation leads to the failure of horizontal bearing capacity, indicate that when the slope is rock, the horizontal bearing capacity of pile foundation is mainly. The slope mainly affects the positive bearing capacity. When the slope changes from 15° to 30°, the positive bearing capacity increases by 41.3%, while the negative bearing capacity only increases by 0.15%. The slope strength has an impact on both positive and negative bearing capacity. The pile-rock elastic modulus ratio changes from 2.8 to 0.9, the positive bearing capacity increases by 80.7% and the negative bearing capacity increases by 73.5%.
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Field test study on vibration reduction effect of blasting barrier hole during excavation of foundation pit

Lv Anlin, Zhang Kai, Wu Zhengyu, Wang Jianxin, Fan Baitong, Peng Qi, Zhu Jianbo

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In order to reduce the dynamic disturbance of adjacent structures caused by blasting construction of foundation pit by using blasting, field test to study the vibration reduction law of the blasting barrier holes was conducted relying on the blasting construction project of foundation pit of No. 1 comprehensive well of Shenzhen Metro Line 16. Based on monitoring of the vibration of ground under the condition of different blasting barrier hole parameters, the influence of blasting barrier hole on peak velocity and dominant frequency of particle vibration on the ground and the influence of parameters of blasting barrier hole on its vibration barrier effect was analyzed. And the following conclusions were draw. Firstly, when the diameter of the blasting barrier hole increases, the vibration isolation rate of vibration barrier hole (VIR) in horizontal radial and horizontal tangential directions increase first and then decrease, the VIR in vertical direction increases and the VIR based on resultant velocity increases. Secondly, the VIR decreases first and then tends to be stable with the increase of the row spacing of the damping vibration barrier holes. Thirdly, when the proportion of water filling in the blasting barrier hole increases, the VIR in horizontal radial direction decreases, the VIR in horizontal tangential and vertical directions increase first and then decrease, and the VIR based on resultant velocity increases first and then decreases.
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Study on Fatigue Feature of Structural High-Strength Rivets in Ring Flange Connections of Wind Turbine Towers

FAN Ke, DAI Kaoshan, HENG Junlin, WANG Rui, LIAO Guangming

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The structural high-strength (HS) rivet demonstrated advantages including preload stability and excellent resistance to the loosening, fatigue and delayed fracture. Thus, the HS rivet has become a promising alternative to the HS bolt currently employed in the ring-flange connection of wind turbine towers. However, relevant studies are still lacked and required on the fatigue performance of HS rivets in ring-flange connections. The work carried out comparative model fatigue tests and refined numerical analysis on the ring-flange connection with HS rivets, in order to investigate its fatigue feature and deterioration mechanism. At first, based on the load transfer feature of ring flange connections, model fatigue tests of twelve specimens were conducted after the static tensile test. The tested twelve specimens included six with HS rivets and six with HS bolts. Further, multi-scale finite element analysis was performed with refined models, in accordance with the local strain-based SWT fatigue evaluation approach. According to the result, the first engaged thread of rivets/bolts is prone to fatigue failure in both the two types of specimens. Under the 2 million loading cycles, the equivalent fatigue strength of HS rivet specimens shows a mean value of 68.9 MPa, which increases by 32.2% compared with the value (52.1 MPa) of HS bolt specimens. The stress concentration at the root of threads could be effectively mitigated due to the flattened thread and increased contact area of inner-outer threads between the sleeve ring and HS rivet. Consequently, the fatigue performance of HS rivets is enhanced. As above, this study suggested that in the fatigue check of ring-flange connections with structural HS rivets, the fatigue strength of HS rivets could be determined as FAT 56, in accordance with the power constant of m = 3.
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Study on the influence of stress principal axis variation on the anisotropy behavior of silty soil in the Yellow River flood area

Zeng Changnü, MA Yuan, YIN Hang, GU He, Wang Yuke

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A series of hollow cylinder torsion shear tests were conducted for the silty soil in the Yellow River flood area, considering the effect of drainage shearing with fixed large principal stress direction. The shear stress-strain behavior as well as the anisotropy characteristics of silty soil were then presented. Under different intermediate principal stress coefficient b and major principal stress direction angle α, the stress-strain relationship and the corresponding shear stress ratio of silty soil were obtained. It was concluded that the value of and have a significant effect on the octahedral stress-strain and the shear stress-major principal strain. The obvious anisotropic character was observed, especially under or 1. Compressed deformation usually occurred in the major principal strain direction. Under a fixed α, the smaller shear strength occurred under a larger value. The peak shear strength and the corresponding axial strain were the largest under the conditions of α=45° and b=0.5, corresponding to the largest
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Study on strength characteristics of sand by GGBS+MgO

陆加越

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Sandy soil is a common geotechnical material. To satisfy the mechanical and environmental requirements in engineering, the granulated blast furnace powder (GGBS) as a solid waste discharged by steel industry can replace cement as a soil curing agent. In this study, GGBS was used as curing agent and magnesium oxide (MgO) was used as stimulating agent to reinforce the sand. The influence of curing age (3, 7, 14, 28, 56 days) and the mixing amount of curing agent (8%, 10%, 12%) and the amount of magnesium oxide (0%, 5%, 10%, 15%, 20%, 40%) on the strength development rule of curing soil were analyzed. The results showed that under the same amount of curing agent, the unconfined compressive strength of cemented sand has no obvious relation with curing age less than 7 days. However, when the curing age was longer than 7 days, the longer the age period was, the higher the unconfined compressive strength of the sand soil was. Furthermore, the amount of curing agent is positively correlated with the unlimited compressive strength of sand. Finally, although magnesium oxide dosage can promote the improvement of the unlimited compressive strength, excessive magnesium oxide would inhibit the increase of the unlimited compressive strength in sand. The strength characteristics of GGBS-MgO treated sand were studied in laboratory experiments, which can provide a theoretical basis for field engineering application.
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Study on bearing capability of concrete-filled pultruded GFRP combination columns tube with different restraints of CFRP

Yang Wenwei, Zhou Haiyang, Wang Tongkuai, Chen Zhiwei

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In order to improve the carrying capacity of the pultruded glass fiber reinforced plastics (GFRP) tube, five specimens were produced with carbon fiber reinforced plastics (CFRP) cloth with different restraint methods and axial compression tests were conducted. The damage mode of this restrained combined column was obtained. Through the analysis of the CFRP restraint effect and the load-bearing performance of this column, the load-bearing capacity calculation model was established. The results show that the squeezed GFRP and the concrete are crushed when the test piece is damaged, some specimens were accompanied by a band tear of CFRP. Disruption morphology increases with the effect of lateral constraint, development from typical cracking fracture to brittle crushing destruction and shear destruction. The bearing capacity of test parts gradually increases with the decrease of CFRP distance, test piece bearing capacity can be greatly improved at a CFRP distance of <100mm, Maximum increase of 1.5 times, when the CFRP spacing is ≥100mm, the improvement of the carrying capacity is not obvious. The change of CFRP spacing and layout mode improved the deformation performance of the test parts significantly, the ductility of the components can be significantly improved. Based on the theory of restrained concrete, the calculation model of specimen bearing capacity established by considering different CFRP spacing and the effect of GFRP bearing action has a high accuracy of calculation results.
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Study on acoustic emission characteristics of concrete and its constituent materials under uniaxial failure

Wang Lizhu, Zhao Yunfeng, Guo Jiahao, Zhang Jiale

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To investigate the relationship between the acoustic emission characteristics of the damage of concrete and its constituent materials, uniaxial compression tests on concrete and its constituent materials (cement mortar and limestone) were carried out and the acoustic emission characteristics of the three during the damage process were statistically analysed. The results show that the peak frequency and amplitude of the acoustic emission signals from all three specimens increase at the time of imminent damage. The frequency distribution of all three shows a normal distribution, with the largest proportion in the 90-120 kHz range. Dynamic b-value trends for cement mortar and concrete do not fluctuate much and remain at a relatively high value range, The dynamic b-value of limestone shows a trend of increasing first and then decreasing, and decreases rapidly near the peak stress, indicating the coming of main fracture. The overall b-value and peak frequency distribution of concrete are between limestone and cement mortar, The overall b-value of cement mortar mixed with limestone is close to that of concrete, this reflects the superposition effect of acoustic emission characteristics of the failure of concrete and its constituent materials.
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Review on the thermomechanical behaviors and constitutive relations of soil

Liu Hong, Xiao Yu, Xiao Yang, Wu Huanran

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Exploitation of the shallow geothermal energy has gradually become a key topic in geotechnical engineering at home and abroad with the rapid development of renewable energy and geothermal heat pump technologies. However, the theory of the shallow geothermal energy falls far behind its application. In particular, the mechanism of soil under the complex coupling of stress and temperature fields remains unclear. For a single soil such as sand, clay, and silt, some results have been found by carrying out the temperature-controlled experiments and proposing the related thermal constitutive models. A certain understanding of the thermodynamic characteristics of soil is got. To promote more comprehensive and in-depth thermal behavior of soil and contribute to more practical promotion and application of the thermal constitutive model in energy engineering, this paper firstly summarizes the experimental research on the thermomechanical properties of soil. Then, the domestic and foreign research progress and status quo of thermomechanical constitutive relations of soil, based on different theoretical frameworks, are reviewed in detail. Thereafter, the application of these thermomechanical constitutive relations in practical engineering is introduced briefly. Finally, suggestions in further research are made, and the development trend of the thermomechanical constitutive relation of soil is discussed and prospected, in view of current existing problems.
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Analytical solution for the deformation behavior of ballastless track under uneven settlement of subgrade

YAN Jianwei, ZHU Zhaoming, LIU Tianyu, TAN Xin, CHENG Chao, HU Yong

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An analytical solution based on non-tension Pasternak foundation composite beam with considering soil shear and interlayer disengaging for the double-block ballastless track, is derived to study the influence of uneven settlement of the subgrade on its deformation. Heaviside step function is introduced to describe the disengaging behavior between the track and the subgrade, and the differential governing equation is solved by finite difference method. A three-dimensional beam-body space finite element model is also established to verify the applicability of the analytical model and determine its scope of application. The results show that when the settlement deformation of the subgrade is relatively gentle, the calculation results of the analytical model and the finite element model are almost indistinguishable, the deviation of the two models is getting larger as settlement of the subgrade exacerbated; For a given subgrade settlement wavelength of 20 m, when the settlement amplitude reaches larger than 21 mm, the analytical model is not applicable; Under the given condition that settlement amplitude of the subgrade is 20 mm, the analytical model is applicable to the subgrade settlement condition with a settlement wavelength greater than 19.8 m.
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Aging effect on physical properties of bentonite under high temperature-strong alkaline conditions

zengzhaotian, zhanghanbin, lvhaibo, panbin, chedongze

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During the operation of the deep geological repository, the bentonite as a buffer material will be in a high temperature-strong alkaline environment for a long time, and its physical properties will deteriorate with time. Aging effect on physical property of MX-80 bentonite powder at high temperature and strong alkali conditions was investigated in this paper. MX-80 bentonite was subjected to alkali-heat conditions, i.e.,T=90°C and CNaOH=0.5mol/L for a time duration of 0, 15, 30, 45, 60, 90 days. The variation of physical properties such as the specific gravity, specific surface area and swell index of MX-80 bentonite was studied through laboratory experiments. Some representative specimens were selected for X-ray diffraction (XRD) tests and thermogravimetric analysis (TGA) tests to provide a reasonable explanation from microscopic perspective. The results showed that the specific gravity, specific surface area and swell index of bentonite decreased sharply from 0 to 45 days, gradually levelling off after then, finally, the reduction amplitudes were 13.6%, 18.5% and 58.1% after 90 days, respectively. Montmorillonite content decreased and albite content increased. The changes of montmorillonite and albite were -23.3% and +3.7% after 90 days. The content of free water, weakly bound water and strongly bound water decreased, and the content of the three decreased by 2.84%, 0.13% and 0.24% respectively after 90 days. The fundamental reason for the deterioration effect of bentonite physical properties over time under high temperature and strong alkali conditions was the dissolution of montmorillonite. The decrease in montmorillonite content leaded to a decrease in specific gravity, swell index and specific surface.
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Experimental study on the influence of cement on the mechanical strength of granite residual soil

TANG Lian-Sheng, HE Yun-Fan, SUN Yin-Lei

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The cement has an important influence on the mechanical properties of granite residual soil. Kaolinite powder, montmorillonite powder, illite powder and red clay powder are used to replace the fine particles of granite residual soil to make remolded soil samples. Compression, shear, tensile and disintegration tests are carried out respectively to study the effects of different cements on the mechanical strength of soil. The results show that the soil particle aggregates after kaolin treatment are increased, and a skeleton structure with high strength is formed between the aggregates. However, the existence of a large number of pores between the skeletons provides a channel for water intrusion, resulting in enhanced water absorption of the soil. Benefiting from the swelling property of montmorillonite in water, the treated soil surface has fewer pores and dense structure, and the expansive body provides high strength cementation capacity, which makes the mechanical characteristics of soil significantly improved. The mechanical strength of the soil sample treated with illite is low, but the soil surface appears relatively dense. From the perspective of the particles dispersed on the soil surface, illite powder is more used as fine material to fill the pores between large particles than as a cement with high strength between soil particles. After physical compaction, the occlusion between particles is enhanced due to compression; At the same time, after a long time of hydration reaction, the cement formed bridge cementation on the particle surface. Under the combined action of physics and chemistry, the mechanical strength of soil has been greatly improved. The type of cement will have a great impact on the mechanical properties. On the one hand, it depends on the characteristics of the cement itself, such as the water swelling characteristics of montmorillonite. On the other hand, it depends on the binding effect of the cement on the soil. The compressive, shear, tensile and collapse resistance of the soil sample are controlled by the binding mode of the cement and the soil sample. This study can provide theoretical and technical guidance for the engineering improvement of granite residual soil.
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Bond strength prediction method of ribbed FRP bars in concrete

Heng-lei Dong, Dongfeng Li, Qingsen Cai, Daiyu Wang

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Until now, there has been limited research on the bond behavior of ribbed Fiber-Reinforced Poly-mer (FRP) bars. In the paper, bond test data of the spirally-glued FRP bar and mechanically-grooved FRP bar were collected to investigate the test parameters on the bond behavior. Results show the macroscopic failure mode for the two types of ribbed FRP bars is pullout failure. More specifically, spirally-glued FRP bars mainly exhibit shearing off of FRP bar ribs, while slight dam-age occurs in concrete. Most grooved FRP bars show shearing off of concrete ribs, and bond strength increases with the increase of concrete strength for both FRP bars. Spirally-glued FRP bars show higher bond strength by increasing concrete cover which contributes to better confinement to FRP bars, but this seems to have no effect on grooved FRP bars. Bond strength of spirally-glued FRP bars can be improved by increasing relative rib height hrd and FRP bar rib width ratio FR. While grooved FRP bars are almost unaffected by hrd, and are mainly influenced by concrete rib width ratio CR, having higher bond strength by increasing CR. The calculated results by the pro-posed equations are in good agreement with the test results with greater accuracy than the design codes. This is because the effect of rib forming process and geometrical features of ribbed FRP bars on bond strength is accurately accounted in the proposed equations.
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Experimental analysis on shear contribution of CFRP sheet to reinforced concrete beams without stirrups

Jin Liu, Jiang Xuan Ang, Du Xiu Li

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The shear failure mode and failure mechanism of 12 CFRP-strengthened concrete beams without stirrups were analyzed. The stress-strain curves of CFRP beams in the whole process were obtained. The quantitative effects of structural size and CFRP ratio on shear strength of CFRP are discussed. Furthermore, a formula for calculating the shear strength of CFRP is proposed and compared with the test results, the test results of others and the standard results in this work. It is found that the structural size has a significant influence on the shear strength of CFRP. The nominal shear strength of CFRP decreases significantly when the structural size increases. In addition, when the beam depth changes from 300 mm to 1200 mm, the nominal shear strength of CFRP decreases by about 50%, which has obvious size effect. Furthermore, under different cross-section sizes, the nominal shear strength of CFRP increases with the increase of CFRP ratio〖 ρ〗_f , but with the increase of CFRP ratio〖 ρ〗_f, the increase amplitude of nominal shear strength decreases, showing a nonlinear growth trend. Finally, the established formula for calculating the shear capacity of CFRP could predict the shear capacity of CFRP under different CFRP ratio and section size scientifically.
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Influence of UFC on cement-soil in peat soil Environment of Dianchi Lake

caojing, sunhuafeng, huangsiyang, kongcheng, liufangyi, liufuhua, tianlin, zhuweiming

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The treatment of peat soil foundation in Yunnan surrounding Dianchi Lake and Erhai Lake poses more and more complex problems for actual engineering projects. It is no longer enough to rely on ordinary cement to reinforce peat soil. This experiment prepares cement-soil samples by mixing humic acid (HA), cement, and ultrafine cement (UFC) into the low organic matter alluvial cohesive soil (blending method). Then, the test method of soaking it in fulvic acid (FA) is used to simulate the cement-soil in the peat soil environment (steeping method). This study performed unconfined compressive strength (UCS) and scanning electron microscope (SEM) tests on samples soaked for 28 days and 90 days, analyzing the influence of UFC proportion on the strength of cement-soil in the peat soil environment. The test results are as follows. Without considering the effects of HA and FA, incorporating UFC can significantly improve the UCS of cement-soil. The rapid hydration of the fine particles to generate a large number of cementitious products improves the cohesion of the soil skeleton and fills the pores. However, when the proportion of UFC increases, the aggregate structure formed by too many fine particles reduces the hydration rate and degree of cement hydration, making the UCS growth rate of cement-soil insignificant. In the peat soil environment, HA significantly weakened the UCS of cement-soil in both physical and chemical aspects. However, UFC can weaken the adverse effect of HA on cement-soil by its small particle size, high surface energy, and solid binding ability. In addition, FA has a certain enhancement effect on the UCS of cement-soil soaked for 28d and 90d, and the addition of UFC can appropriately promote the enhancement effect of FA on cement-soil UCS. SEM test results showed that cement hydration products increased significantly with the increase of UFC proportion. The cementation between hydration products and soil particles is significantly enhanced. The size and connectivity of cement-soil pores are significantly reduced, and the structural integrity is enhanced.
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Experimental study on the road performance of slurry shield tunnel residue improved by industrial waste residues

GUO Qin-ying, LI Bai-yun, DING Jian-wen, CHEN Jian-gang, SUN Shuai, MA Yun-long

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This study is carried out to realize the resource utilization of mud water shield residue. Industrial waste residues such as alkali slag and desulfurization gypsum are reasonably used to be combined with the traditional lime, in order to convert waste mud into qualified roadbed filling materials. Through the laboratory compaction tests, CBR tests, unconfined compressive strength tests, wetting-drying cycle tests and microscopic tests, the mechanical properties, immersion stability and durability of shield tunnel residue improved by lime-alkali slag and lime-desulfurization gypsum were studied, and the improvement mechanism was analyzed. The test results show that the mechanical properties of the soil were improved significantly after compound improvement. The water stability and durability were also greatly improved, with better mechanical properties for road use. Among them, the overall water stability performance and durability of the lime - desulfurization gypsum groups were better than the lime - alkali slag groups. During the wetting-drying cycles, the durability of the specimens mixed with 3% desulfurization gypsum was relatively good, with only small cracks not penetrating the specimens during the cycles. The study shows that the shield tunnel residue has good mechanical properties for road use after compound improvement of lime and desulfurization gypsum, and can be used as roadbed filling materials.
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Micro-cracking mechanism of cement stabilized macadam based on discrete element method

liuzilong, mashibin, hemiao, liangdong, niuzongyue

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To investigate the micro-cracking evolution mechanism of cement stabilized macadam, a numerical model of mesoscale heterogeneous cement stabilized macadam was established. The microfracture network was introduced into the fine-scale inhomogeneous model and the relevant parameters were obtained using unconfined compressive strength tests. Then, the effect of different microfracture parameters on the micro-cracking degree was explored according to the displacement variation of particles in the model under vibration load. Finally, the energy evolution law of the system with different microfracture number was further analyzed. The results indicate that the numerical simulation results are in good agreement with the laboratory test results, the discrete element model of cement stabilized macadam can accurately characterize the mesoscopic failure characteristics of materials. Micro-cracking damage after the secondary vibration load together with the increasing of microfracture width and microfracture number as a result. The microfracture density plays a decisive role in the degree of microcrack for cement stabilized macadam. With the increase of the microfracture number, the elastic strain energy storage capacity of the material decreases, and the total energy input of the cement stabilized macadam decreases. This study has proved that the positive effect of early micro-cracking on shrinkage stress reduction. In addition, the mechanical characteristics and fine mechanism of micro-cracking in cement stabilized macadam materials are revealed.
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Effect of Aluminum ion flocculant on the test of microbial reinforced sand

WEI Ren-jie, PENG Jie, XU Peng-xu, LI Liang-liang

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The excessive number of injections of cementing solution required for MICP limits practical engineering application . In order to reduce the number of injections and improve the efficiency of the cementing process, an enhancement method was investigated in this study in which aluminum ion flocculant was added to the cementing solution to enhance the curing rate and effect of MICP. Experiments were carried out on MICP-reinforced sand columns, and the influence of different concentrations of AlCl3?6H2O to the cementing solution on the reinforcement effect was studied. In the aqueous solution test, the changes of precipitation and solution pH under different solution conditions were observed, and the effects of the aluminum ion flocculant on the composition and morphology of the deposited calcium carbonate were investigated by XRD and SEM tests. The results show that, compared with the control group of conventional methods, after adding an appropriate amount of aluminum ion flocculant into the cementing solution, the proposed method resulted in the experimental sand column being reinforced after 3 treatments of the cementing solution. The unconfined compressive strength reaches 1.7Mpa after 5 treatments of the cementing solution, compared to 10 treatments using the conventional method.
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Parameter prediction of shield slurry separation system of neural network based on wavelet

ZHOU Cuihong, ZHOU Fuqiang, LIU Zhaohe, ZHAI Zhiguo

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When the slurry shield passes through the composite formation, the parameters of the shield tunneling and slurry separation system often fluctuate greatly, influencing construction safety and tunnelling efficiency. It is difficult to extract and deal with the parameters of slurry separation system, there are few studies on the prediction of shield slurry separation system. Base on the Wangjing Tunnel, the coordinated control technology solid-liquid separation of screening, two-stage cyclone, and centrifugal / pressure filtration are adopted according to the stratum conditions, solving the contradiction between shield tunneling and slurry treatment. Collect shield tunneling parameters (tunnelling speed, cutter head speed, total propulsion force, penetration) and slurryr separation parameters (feed and discharge volume, specific gravity, viscosity). Improve data quality through Cook distance outlier detection and wavelet threshold denoising, . The 12 parameters are input specific gravity ratio and viscosity ratio of two-stage cyclone separation, and the output parameters are discharge volume, discharge specific gravity and discharge viscosity，BP neural network was established to predict parameters of the slurry separation system, three different formation rings were selected for prediction and analysis. The prediction results show that the average prediction errors are all within 5%, they still have high accuracy under the composite formation, which provides reference in risk prediction and parameter selection.
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Mechanical properties of steel fiber reinforced alkali-slag recycled aggregate concrete

CHEN Pang, WANG Zhengxuan, Zhang Jianxin, WANG Hui, SHI Zhaoyue

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Alkali slag recycled concrete is a new type of concrete prepared by replacing cement with alkali excited cementing material and natural stones with recycled aggregate, which can effectively reduce the amount of Portland cement and improve the utilization rate of waste concrete. However, there has been no relevant research on its mechanical properties. In this paper, the effects of steel fiber substitution rate and recycled aggregate substitution rate on compressive properties, splitting tensile properties and flexural properties of alkali slag recycled concrete are studied. The results show that: With the increase of recycled aggregate, the cube strength fcu, splitting tensile strength ft and flexural strength fw of recycled alkali slag concrete all decrease, and the reduction range is 30%, 10% and 15% respectively when the substitution rate of recycled coarse aggregate is 100%. The cube strength and splitting tensile strength of alkali-slag recycled coarse aggregate concrete with increase first and then decrease with the increase of steel fiber volume substitution rate. When the steel fiber volume substitution rate is 0.6%, the compressive strength and flexural strength reach the maximum value. The flexural strength of alkali slag recycled concrete increases with the increase of steel fiber volume substitution rate.
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Calculation for vacuum consolidation of dredged slurry considering variable soil column radius

Wu Jianqi, Liu Xiang, Li Min, Fu Hongtao, Li Xiaobing, Cai Ying

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Prefabricated vertical drainage plate (PVD)-vacuum preloading method is one of the effective methods commonly used to improve the dredged slurries. However, in the process of using the vacuum preloading method to improve the dredged slurry, a dense area (soil column) with a gradually decreasing radius from top to bottom will be generated around the PVD, which delaying the soil consolidation rate. Based on the above phenomena, this paper assumed that the soil column radius attenuates linearly with depth, and based on the assumption of equal strain, and the Hansbo's consolidation theory, the consolidation equation considering the change of soil column radius with depth is deduced. At the same time, by calculating the above equation, the influences of the permeability coefficient, the radius of the soil column and the variation of the radius of the soil column along the depth on the soil consolidation rate were explored, and compared with the existing laboratory test data. The result shows that the smaller the permeability coefficient of the soil column, the slower the dissipation of pore water pressure, and the slower the consolidation rate. As the soil column radius gradually increases, the soil consolidation rate gradually decreases. The smaller the residual coefficient after the attenuation of the soil column radius, the greater the attenuation degree of the soil column radius along the depth, the smaller the influence on the soil consolidation in the weak area, and the faster the soil consolidation rate. In the case of considering the soil column radius attenuation with depth, the calculated results in this paper are in good agreement with the experimental results.
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Experimental study and numerical simulation on fatigue crack growth of Q550E high strength steel and welded joint

MA Yafei, CHENG Erxiang, WU Xianshun, HE Yu, WANG Lei

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Welded detail is the weak part of steel bridges. The fatigue damage of welded joint is becoming one of key problems affecting the service safety of bridges under repeated vehicle loads. This study conducted static tensile and fatigue crack growth tests of the base metal and weld joint of Q550E high-strength steel. The fatigue crack growth models of base metal and welded joint were established, and the effects of stress ratio on the fatigue crack growth rate of welded joints of high strength steel were revealed. The coupled simulation method FRANC3D and ABAQUS was performed, and the key influence parameters were determined by sensitivity analysis. The results show that the FCG rate parameter m increases with the increase of stress ratio. The FCG rate parameter lgC and the threshold stress intensity factor range decreases. The parameter m of butt weld specimen is about twice that of base steel. The threshold stress intensity factor range of weld joint is larger than the base steel and more sensitive to the stress ratio. The developed coupled simulation method can accurately predict the fatigue life of high-strength steel welded joints. The specimen thickness and initial crack depth have a significant impact on the fatigue growth under a high stress ratio.
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Preparation and Filling Effect Verification of Phosphogypsum Particles

Huang wan, Tan Yunzhi, Chen Junlian, Wu Chiqiu, Lv Wei

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Preparing phosphogypsum for building materials is an effective way to consume phosphogypsum on a large scale. However, direct incorporation of phosphogypsum in powder form poses a risk of non-point source contamination. To this end, the paper proposed to prepare pressed particles with phosphogypsum as the main raw material. Meanwhile, cement was used as a cementitious material, and the filling samples were prepared by adding these particles, and the tests such as compressive strength, determination of phosphorus (fluorine) pollutants, pore structure analysis, and microscopic morphological analysis were carried out to verify the filling effect of these particles. The results show that the strength performance of particles-filled samples is better than that of powders- filled samples, and their phosphorus (fluorine) fixation effect is also superior, after soaking for 90 days, the fluoride concentration in the leaching solution of particles-filled samples is 0.035 mg/L, and the phosphorus concentration is 0.35 mg/L, both of which meet the first-level emission standards, and the excellent performance of particles-filled samples is explained by pore structure analysis and microscopic morphological analysis. This research has successfully verified that phosphogypsum has a good filling effect when filled with building materials in the form of particles.
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Research on damage identification method of PE sheath of bridge stay cable based on lightweight convolutional neural network

Liu Xiao-Yu, Huang Yong, Xu Feng, Li Hui

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In recent years, deep neural network and computer vision techniques have played an increasingly important role in structural health monitoring. In this paper, deep learning technology is used to identify the PE sheath damage through the image data of bridge stay cable damage collected by UAV. This paper aims to realize the intelligent and rapid identification of local damage on the surface of stay cables of long-span bridges on devices with low computational ability, and solve the problems of relatively low computational efficiency and large scale of model parameters in the current research of traditional deep convolution neural network. A lightweight region proposal convolution neural network model is proposed. Firstly, the theoretical basis of region proposal network and its lightweight improvement method is introduced, and the necessity of lightweight model processing is analyzed. It reduces the performance requirements of devices for model training and prediction under the premise of ensuring identification accuracy, achieving the purpose of saving computational resources and time. Secondly, the problem of insufficient data of damage samples is solved by multiple means of data augmentation. The contrast experiment and the analysis of statistical results verify the superiority of the lightweight neural network model. The results show that the lightweight network can improve the complexity and quantity of calculation of the model to a large extent under the premise of a small sacrifice of recognition accuracy. It effectively expands the practicability of the neural network in engineering applications.
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Experimental study on flocculation-solidification combined with vacuum preloading treatment of waste mud

HAN Chao, YU Yuezhong, BAI Bin, DONG Chaoqiang, ZHANG Rongjun, FAN Zhou, WU Wei, SUN Ke

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After flocculation conditioning and chemical solidification, the initial bad engineering characteristics of high water content mud can be improved. If waste mud is to be recycled into embankment filler, it is bound to have certain requirements on the strength of the treated mud. In recent years, the authors have explored and proved that the vacuum preloading-flocculation-solidification combined method (VP-FSCM) can effectively treat mud slurry with high water content (> 300%) and transform it into embankment filler. This study has carried out a series of laboratory model tests, on the one hand, to explore the feasibility and high efficiency of VP-FSCM process for treating waste mud (water content is about 150~300%); On the other hand, to optimize the formulation (type and dosage, etc.) of VP-FSCM process in waste mud treatment. The test results show that: (1) The undrained shear strength of the waste mud treated by VP-FSCM after 28 days is 2.76 times that of the waste mud treated by flocculation-solidification combined method (FSCM), which proves the high efficiency and feasibility of VP-FSCM. (2) The results of dehydration / settlement characteristics and mechanical characteristics show that the best additives for treating waste mud by VP-FSCM process are cement (OPC), ground granulated blastfurnace slag (GGBS), quicklime (CaO) and polyacrylamide (PAM), and their optimal contents are 5%, 5%, 1.5% and 0.12% respectively. (3) Under the condition of the best additive type and dosage, the higher the vacuum pressure, the higher the strength of the treated waste mud and the lower the moisture content after curing.
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Calculation Method for Support Distance Determination under In-Situ Protection of Buried Box Culverts

dengshengjun, hudong, liuheng, fuli, linhuanyu, jianggang

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Underground power pipelines are often buried in the soil in the form of box culverts. When such existing pipelines are involved in underground construction, the in-situ support protection method is generally used to ensure the stability of the box culvert during the construction process. The determination of the distance between the support points mainly depends on the engineering experience. In this paper, considering the cross-sectional properties of the box culvert and the settlement effect in the soil, the mechanical models of the middle-span and the side-span of the box culvert are respectively established, the vertical displacement of the box culvert is calculated, and the allowable support points are deduced. Based on the maximum spacing value, a calculation method for the spacing between the support points of buried box culverts under in-situ support protection is proposed, and the accuracy and engineering of the calculation method are verified by a case of the in-situ protection project of large-diameter pipe culverts at Yunnan Road Station of Nanjing Metro Line NO. 5. Applicability, meanwhile, the full-span longitudinal deformation law and parameter sensitivity of the buried box culvert are further analyzed through numerical simulation. The research shows that: the spacing between the supporting points of the box culvert side span is 8m, the spacing of the middle span is 8.73m, and at least 12 supporting points need to be set for the whole span. Within the range of three times of parameter magnification, with the increase of reinforcement depth, width and soil compressive modulus, the displacement of the box culvert gradually decreases; the calculation method of the distance between the support points of the buried box culvert can provide a reference for the design of similar projects.
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Study on unconfined compressive strength of phosphogypsum/lignin solidified lead contaminated soil

zhao zhi, Yang xiujuan

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Industrial solid waste phosphogypsum and lignin were used to solidify the artificially formulated lead contaminated soil. Through the unconfined compressive strength test, the effect of curing agent dosage and curing age on the stress-strain curve, failure pattern and unconfined compressive strength of the soil with different levels of lead contamination after solidification were investigated, and the curing effects of the two curing agents were compared and analyzed. The microscopic characteristics of soil samples before and after curing were analyzed by scanning electron microscopy test. The results show that both phosphogypsum and lignin can increase the unconfined compressive strength of stabilized soil and reduce the failure strain. The unconfined compressive strength of solidified soil increases continuously with the increase of phosphogypsum content, and increases first and then decreases with the increase of lignin content. Extended curing time can effectively improve the unconfined compressive strength of stabilized soil. With the increase of dosage and curing age, the internal cementation level of soil increases, and the failure pattern of soil sample gradually changes from local tension cracking to shear failure, showing brittle failure characteristics. The two curing agents have their own advantages and disadvantages in curing soil. Lignin is better than phosphogypsum in curing high concentration lead contaminated soil and has better resistance to deformation, while phosphogypsum has better ability to improve strength and fix lead in a short time. Scanning electron microscope (SEM) test shows that the curing agent can fill the pores and cement soil particles, and the hydration products form a dense structure in the soil, which is macroscopically expressed as strength enhancement.
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Research on lateral earth pressure and load-reducing effect behind retaining wall with EPS cushion and light-weight soil

XU Xiaoliang, WANG Xinpei, ZENG Linfeng, ZHANG Tingfeng, QIAO Suyun

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Laying a flexible cushion or backfilling lightweight soil behind the retaining wall has important engineering significance for its optimized design and cost reduction. By carrying out model tests of retaining walls with different level of loads, the magnitude and distribution characteristics of the lateral earth pressure when laying EPS flexible cushion, backfilling lightweight soil and applying it at the same time are analyzed, and the load-reducing effect is discussed. The result shows: when the retaining wall is paved with flexible cushion, backfilled with lightweight soil, or both are applied, the lateral earth pressure shows a "bulging" nonlinear feature that increases first and then decreases with the burial depth, and the maximum value of earth pressure often appears at half of the wall height; under the same load, the load-reducing effect of backfilling lightweight soil is relatively weak, the load-reducing rate is 10%-25%, the maximum load-reducing rate of laying a flexible cushion is increased by 1.5 times compared with lightweight soil, when both two are applied, the load-reducing effect is the strongest, and the maximum load-reducing rate is increased by nearly 3 times; the load-reducing effect of the flexible cushion decreases with the variation of thickness, the foam content is more sensitive to the load-reducing rate of the backfill lightweight soil. In the engineering project, a medium-thickness cushion is optimal choose, if the applying load of the backfill is large, the content of the backfill lightweight soil can be appropriately increased.
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Study on water vapor adsorption characteristics of unsaturated loess

FU Wenyuan, LIU Deren, WANG Xu, LI Jiandong, MA Yue

Abstract: (55) HTML (0) PDF (0.00 ByteKB) (0)

In order to study the adsorption characteristics of water vapor on unsaturated loess, isothermal adsorption experiments under different humidity conditions were carried out by vapor equilibrium method. The adsorption behavior of water vapor on unsaturated loess surface was analyzed, and the effects of temperature, mineral composition and content, dry density on the adsorption property of soil were discussed. The experimental results show that the water vapor adsorption capacity of unsaturated loess increases with the increase of relative humidity, and the whole process includes three stages: monolayer adsorption, multilayer adsorption and capillary condensation. The GAB model can be used to describe the water vapor adsorption process of unsaturated loess. There is a significant negative correlation between water vapor adsorption and temperature. When the relative humidity is constant, the adsorption capacity of water vapor decreases with the increase of temperature. Water vapor adsorption of unsaturated loess is closely related to mineral composition, and clay mineral content directly affects its water vapor adsorption capacity. In addition, the effect of dry density on water vapor adsorption can be divided into two stages. When the relative humidity RH<80%, water vapor adsorption capacity increases with the increase of dry density. Until entering the capillary condensation stage, with the increase of dry density, the amount of water vapor adsorption no longer increases but decreases.
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Experimental study of engineering waste slurry treatment by vacuum thermal consolidation combined with dynamic compaction

WU Jianqi, TAO Jianwei, FU Hongtao, Li Xiaobing, ZHOU Chenyang, CHEN Teng

Abstract: (96) HTML (0) PDF (0.00 ByteKB) (0)

In order to solve the problem that heat and vacuum negative pressure decrease in soil which leads to uneven reinforcement effect during vacuum thermal consolidation, the vacuum thermal consolidation combined dynamic compaction method is applied in the reinforcement treatment of engineering waste slurry utilize the characteristics of soil compaction can be improved by dynamic compaction method. The influence of different tamping time on the reinforcement effect of soil was studied by conducting four groups of model tests.. The results show that when the settlement rate is 4cm/3d, the tamping time is the best, the average settlement of soil surface is 26.5%, 11.72% and 3.74% higher than that of other test, and the treatment effect of engineering waste slurry is the best, which can effectively solve the poor reinforcement effect of deep soil under vacuum thermal consolidation and improve the uniformity of soil. Combined with the results of microstructure analysis, it can be found that due to the redistribution of pores between soil particles, the soil density is higher, and the shear strength increases accordingly under the appropriately tamping time. In addition, the drainage channels formed by the micro-cracks generated by the redistribution of internal pores can promote drainage and further improve the consolidation effect.Therefore, the shear strength and consolidation degree of the soil can be promoted under the appropriate tamping time.
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Experimental Study on the Stabilized Excavated Sludge Based on Structural Support-Solidification Technology

shao jicheng

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To dispose sludge and construction waste, and make their common resource utilization,construction waste was added to the sludge according to 15% of the mass ratio of the sludge as aggregate, and the in-situ solidification experiment of the sludge was carried out in field.?The test results show that when the content of solidified agent is 8%, the strength of solidified sludge is pretty high, and the laboratory unconfined compressive strength of solidified sludge can reach 320kPa after curing for 28 days. The in-situ solidification experiment in field shows that the characteristic value of soil bearing capacity is 149kPa estimated by cone penetration test when the content of solidified agent is 8%. And the characteristic value of soil bearing capacity measured by plate loading test is 190kPa, which has obvious solidified effect on sludge. With low dose solidified agent, the structure effect of aggregate is not obvious. When the content of solidified agent is 8%, the structure effect of aggregate is beneficial to improve the bearing capacity of solidified sludge and the characteristic value of soil bearing capacity can reach 325kPa. The improvement rate of solidified sludge by structure effect is 71.05%, and the compression modulus of solidified sludge is 55.02%.
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State-of-the-art research of bridge thermal action and effects in 2020

xiaolin

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Temperature action is one of the important loads in bridge construction and operation stages. With the extension of traffic network, severe climate could be expected to cause larger temperature action than those recommended in the specifications. The complexity of traffic environment also increases the probability of bridge fire and related damage. In-depth study of bridge ambient and fire temperature field, and identification of its actions and effects can ensure the safety of bridge from the aspects of design, construction and maintenance. This study reviews the latest domestic and overseas research on ambient temperature action, temperature effect and bridge fire action in 2020, and prospects the hotspots and directions of the future research of bridge thermal action and effects.
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State-of-the-art review of timber bridge in 2020

Zhao Ran, Zhang Rui, Hu Peng, Chen Kedao

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Timber bridge is a kind of bridge built with timber as the main building material, which is eco-friendly, lightweight and aesthetic, convenient for construction, and reliable in performance. In recent years, as the gradual recovery of forest resources in China, and the processing, anticorrosion and connection technologies of modern timber structure are improving continuously, timber bridge has become an ideal type of middle and small span bridge. To better adapt to the current situation of bridge construction and promote the application of wooden bridges, in this paper, the application status of timber bridge, timber decking technology, the detection and strengthening technology, timber-concrete combined bridges and other aspects are summarized. Hoping to assist the reference of practitioners in the industry.
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State of the art on prefabricated concrete bridge structures in 2020

XuZIYi, ZhangZiyang, XuTengfei

Abstract: (636) HTML (0) PDF (0.00 ByteKB) (0)

Prefabricated bridges have become an important development direction of bridge construction due to the advantages of good construction quality, low impact on the environment, short on-site operation time, and high level of construction safety. Prefabricated concrete bridges are not only suitable for urban road bridges with complex traffic, but also for railway bridges in difficult construction environments. This paper sorts out the research progress of prefabricated concrete bridges at home and abroad in 2020 through the method of literature research. According to the type of bridge structure, new technologies, new structures and typical engineering applications in this field are discussed from two aspects: the upper structure and the lower structure. After a rough summary in this article, in the superstructure, the connection structure, crack resistance and durability of the nodes have received extensive attention from scholars; in the substructure, as the prefabricated system is applied to the bridge in the high-intensity earthquake area, The structure and seismic performance of prefabricated bridge piers are currently a hot research topic. The durability and crack resistance of the substructure still needs to be improved.
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Research progress of Bridge Assessment and reinforcement in 2020

zhangfang

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Due to the contradiction between the demand of bridge construction brought by the rapid economic development and the backward technical reserve in the period of large-scale construction, China will face the increasing pressure of bridge maintenance in the next 10 to 30 years. Based on the latest research progress in the field of bridge evaluation and reinforcement, this paper introduces the chemical and physical methods of the main bridge disease monitoring technology, the bridge health monitoring technology and equipment including sensor technology and signal processing technology; The bridge health evaluation method based on time-varying reliability theory and historical data is compared, and the significance of structural parameter inversion relative to artificial intelligence is discussed; The partial reinforcement methods for bending, shearing and seismic resistance, the integral reinforcement methods for additional structural systems, and the electrochemical chlorine removal technology are introduced. The decision-making methods of maintenance and reinforcement of network level and project level are introduced. Considering the cross-disciplinary characteristics, some advanced sensor, signal processing technology and evaluation theory are also introduced in order to clarify the internal logic, may be able to play a certain inspiration and train of thought inspiration.
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State-of-the-art review of planning and protection of bridgeCultural heritage in 2020

Zhang Fang, Deng JieChao, Zhang Kaiquan, Yang Qian, Qian Yongjiu

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In the process of cultural integration in the world, all countries pay more attention to the protection of their cultural heritage. As a kind of heritage of comprehensive human activities, bridge cultural heritage has many attributes such as transportation heritage, architectural heritage, urban planning heritage, industrial heritage, etc., and has been paid more and more attention by all countries in the world. However, at present, compared with other cultural heritages, the research and practice of bridge cultural heritages in the global scope are still immature and have not formed a system. Through the statistics of ancient bridge, ancient bridge culture and related research in the past 20 years in China, we can clearly see the overall status of bridge cultural heritage research in China. Moreover, based on the induction and analysis of the research results of bridge cultural heritage at home and abroad in 2020, the paper expounds and summarizes the research progress of bridge cultural heritage at home and abroad in 2020, and looks forward to the planning and protection of bridge cultural heritage in the future.
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Research progress on fatigue of steel bridge in 2020

Zhang Qinghua, Lao Wulue, Cui Chuang, Bu Yizhi, Xia Song

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Steel bridge has outstanding advantages, such as high ratio of strength to weight, large span capacity, easy to factory manufacturing and assembly construction, where bridge engineering is going in the further. However, the engineering practice shows that fatigue and fracture are the decisive factors to reduce the service performance of steel structure and cause catastrophic accidents, which seriously restrict the development and application of steel bridges. The in-depth and systematic researches on this practical engineering problem from different perspectives have been have conducted at home and abroad. To clarify the urgent problems and determine the research focuses and development directions in the next stage, the latest research progress in fatigue of steel bridge are summarized, including fatigue failure mechanism and fatigue resistance assessment method, anti-fatigue design and construction technology, environmental factors and their effect mechanism to fatigue resistance, fatigue crack identification, monitoring and detection, fatigue crack treatments and fatigue performance enhancement. The results demonstrate that the fatigue issue is a hot topic to researchers and engineers. the researches on fatigue critical problems in steel bridge has made adequate progress. Based on the studies including anti-fatigue design method, structures with high fatigue resistance, fatigue resistance assessment method, construction technology, fatigue damage monitoring and fatigue micro-crack identification, remaining fatigue life prediction and fatigue performance enhancement, it is the research emphasis and future directions to establish the fatigue resistance technology of steel bridges in life cycle.
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Research progress of explosion and fire resistance of bridges in 2020

cuichuang, Yang Zhengxiang, Wang Hao, Zhang Qinghua, Bu Yizhi, Xia Song

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The demand for energy exchange increases as the rapid development of regional economy, and the number of vehicles loading and transporting "burning, vapour, explosion and chemical" dangerous chemicals is increasing. The structural safety of bridge in-service is seriously threatened due to the explosion and fire caused by the vehicles emerge in an endless stream. As a hot topic in the field of bridge disaster prevention, scholars at home and abroad have made fruitful research in the field of bridge explosion and fire resistance. Based on the publications in 2020, this paper briefly summarizes the research results at the present stage. This paper focuses on the explosion impact load test and numerical simulation method, bridge fire test and simulation technology, bridge anti-explosion performance and deterioration mechanism, bridge damage mechanism and safety assessment under fire, bridge anti-explosion safety assessment method, bridge performance evolution and disaster mechanism after overfire. The explosion test technology at present through the analysis of the system and research the mechanics characteristics of structure under high strain rate, complicated fire environment temperature transmission and distribution, coupled damage evolution of the bridge subjected on multi-disasters, disaster mechanism and bridge structure safety assessment system are of lack and urgent need. In order to ensure the service safety of bridge structure in the whole life cycle, the structural characteristics and operation and maintenance safety under extreme load conditions such as explosion and fire have been is of primary importance in the operation and maintenance of bridge.
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Research progress in 2020: vibration and noise reduction of rail transit bridges

Li Xiaozhen, Zheng Jing, Bi Ran, Zhang Xun, Luo Hao, Cao Zhiyang

Abstract: (274) HTML (0) PDF (0.00 ByteKB) (0)

With the rapid development of high-speed railway and urban rail transit, the problems of vibration and noise become more and more prominent. The noise mitigation of traditional vertical sound barrier was obvious on wheel rail noise, but is insufficient when the train speed exceeds 250 km/h. Therefore, fully enclosed sound barrier is pushed the construction alongside high-speed railway In recent years, steel bridges or steel-concrete composite bridges have gradually been widely applied in high-speed railway and urban rail transit. Steel bridges or steel-concrete composite bridges have greaterer sound radiation ability, wide spectrum, large amplitude and difficult to control. Therefore, it is urgent to solve the noise radiation issue wheng steel bridges or steel-concrete composite bridges are built in environmentally sensitive areas. Focusing on the two study directions of "noise reduction performance and dynamic characteristics of high-speed railway sound barrier" and "vibration and noise reduction of steel bridge", the research trends and development trend of this direction are briefly reviewed in this article.
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State-of-the-art review of the Numerical simulation of ridge structure in 2020

zhoulingyuan

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Zhou Linyuan (School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031，China) Abstract: With the development of computer technology and in-depth study of computation theory, numerical analysis has become the major analysis method for bridge structure. At present, through the numerical simulation of bridge structure, the mechanical behavior and response under various complex actions can be obtained, with which the calculation efficiency and adaptability are far higher than those of analytical method and model test. Based on the relevant research results at home and abroad in recent years, the application of numerical analysis technology in bridge structure analysis and the latest research results are summarized. This paper mainly focuses on the finite element numerical simulation technology related to the analysis of the main mechanical behavior of bridge structure, including the latest research direction of beam theory, the nonlinear analysis methods and technologies, the research progress of a variety of numerical constitutive models for bridge structure materials, and the timeliness of Mechanical properties of bridge structures under corrosive environment. The new development of finite element method and numerical simulation method of composite structure based on beam theory are summarized. Finally, the problems that need to be further studied and solved in this field are analyzed and prospected.
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State-of-the-art Review of Vehicle-Bridge Coupling Vibration in 2020

Li Xiaozhen, Wang Ming, Jin Zhibin, Zhu Yan, Qiu Xiaowei

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The main research contents of vehicle-bridge coupled vibration include vehicle-bridge coupled vibration and random vibration under the effect of track irregularity, wind-vehicle-bridge coupled vibration, earthquake-vehicle-bridge coupled vibration, new rail vehicle-track beam coupling Vibration and other aspects. At present, the construction of railway bridges in China is facing new challenges such as larger spans, high speeds, and high comfort levels. Under external excitations such as wind loads and train loads, the vehicle-bridge interaction is becoming more and more significant. How to accurately predict the dynamic response of the vehicle-bridge coupling system and the running performance of high-speed trains in the actual complex wind environment, and provide technical guidance for bridge design, line operation, maintenance and management, and become a research hotspot and development trends in the field of vehicle-bridge coupled vibration in 2020.
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Advances in the Implementation of UHPC-OSD System

Xia Song, Chen Liu, Yang Xu

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Ultra High Performance Concrete (UHPC) is combined with the Orthotropic Steel Deck (OSD) in a lot of projects nowadays. That is a typical example of the implementation of new materials and new structures in bridge engineering. Benefitting from its high stiffness, UHPC slab can evidently reduce the local deformation of OSD. In this way, we can greatly reduce the fatigue stress amplitude and the fatigue resistance is increased. In the present work, we reviewed the research advances on the composite UHPC-OSD system from five aspects: the new structures, the shear connectors, the basic static behaviors of the composite deck, the fatigue performance of the composite deck and the basic mechanical properties of UHPC or UHPC members. Most of the concerned literature was published in 2020 or 2021. However, some works reported in a few other recent years were still mentioned in the present work.
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State-of-the-art review of the bridge health monitoring in 2020

ShanDeShan, LuoLingFeng, LiQiao

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The bridge health monitoring system (BHMS) continuously measures and records the structural responses by using a variety of sensors and communication devices in the bridge operation process. The automatic analysis of signal data can be done effectively in the BHMS to fulfill the timely danger warning and safety assessment. The BHMS leads to the better transportation operation of bridges, the longer service life of bridges, and the more reasonable determination of the bridge management and maintenance for engineers. For the sake of the more efficient application of health monitoring system in bridge engineering, this paper summarizes the current states of several representative BHMS techniques: signal denoising, signal warning, modal parameter identification, finite element model updating, damage identification, condition prediction and assessment. Then, the related researches and applications of these key techniques during 2020 are summarized and discussed. Consequently, it is found that the machine learning methods have been more and more widely used in the current research of key technologies of the bridge health monitoring.
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State-of-art review of the durability of concrete bridges in 2020

ZHAN Yulin, SI Ruizhe, ZANG Yamei

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In recent years, the durability of concrete bridges has attracted extensive attention from researchers and has been one of the hot topics in bridge research. The durability of concrete bridges can affect the safety and service life of bridges directly. Currently, the research on the durability of concrete bridges is mainly divided into two aspects: (1) From the perspective of the damage mechanism of the materials, the damage modes and influence factors of the bridge component materials are studied and the influence mechanism of the durability of the concrete bridge materials is analyzed; (2) From the whole of the bridge structure, the design and evaluation of the durability of the bridge and the maintenance of the bridge are studied, and the methods to improve the durability of the concrete bridge structures are explored. In order to grasp the research trend on the durability of the concrete bridge, this paper reviewed the literature on the durability research of concrete bridges by domestic and foreign scholars in 2020, from the design of the concrete bridge, the durability of the concrete material research, the study of concrete bridge reinforcement corrosion and the durability of concrete bridge improving technology, the influence of different service environment on the durability of the bridge, performance evaluation and service life prediction. The research focus and development direction of the durability of concrete bridges in the future are discussed.
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State-of-the-art research of steel-concrete composite bridges in 2020

Wei Xing, Xiao Lin, Wen Zongyi, Kang Zhirui

Abstract: (356) HTML (0) PDF (0.00 ByteKB) (0)

Steel-concrete composite bridges, one of the sustainable structural forms, have excellent composite technical, economic and social results, and are increasingly popular in the bridge engineering. The steel-concrete composite structure can give full play to the material advantages of concrete and steel, and has been widely used in many fields of structural engineering, because of the reasonable load transfer, the economic efficiency, and the ease of construction. In order to accelerate bridge construction to assemblage, greening and intellectualization, promoting the use of steel-concrete composite structures in small and medium-span bridges faces opportunities and challenges. Two major categories, including research on commonly used shear connectors and steel-concrete composite girders in 2020, are collected, categorized and reviewed. Research on shear connectors covers the basic mechanical properties of stud connectors, PBL connectors, bolt connectors, and improved connectors, as well as the durability and degradation properties of connectors. Research on composite beams includes theoretical models, combined effects and spatial behavior, performance in the negative moment zone, dynamic characteristics of composite beams, deterioration performance, detection and reinforcement, construction methods.
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Research progress of bridge construction monitoring in 2020

yangyongqing, Gaoyufeng, Huangshengqian, Wubinbin

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Bridge construction monitoring is an important part of bridge construction technology, is the key to ensure the quality of bridge construction, is the safety guarantee of bridge construction, has become an important content of research in the field of bridge engineering. By means of literature research, with the keywords of "construction control / monitoring ", "construction control theory / method", "construction monitoring system" and "intelligent monitoring", more than 60 scientific research papers published in 2020 were searched and sorted on Web of Science, Science Direct and CNKI. This paper mainly summarizes the research progress of domestic and foreign scholars in the aspects of bridge construction control theory, construction control parameter identification and state prediction, bridge construction monitoring system and intelligent monitoring, and the hot spots of bridge construction control research in the future were prospected.
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The State-of-the-art in Steel Bridges

zheng kaifeng

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In order to promote the development of steel bridge technology, research hot issues and frontiers in recent years in the field of steel bridges at home and abroad were systematically sorted out. Firstly, it reviews the recent construction achievements and technological progress of large-scale steel bridges in China. Then the latest progress made in the main research directions in the field of steel bridges were systematically summarized. At the same time, many pioneering work done in various aspects of the steel bridge are introduced in detail. It is expected to provide basic information and reference for engineering applications and academic research in the field of steel bridges.
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State-of-the-art review of the bridge foundation engineering in 2020

JIANG Xinyu, WU Shouxin, FENG Jun, LI Xiaogang, LI Yi

Abstract: (133) HTML (0) PDF (0.00 ByteKB) (0)

The foundation of a bridge is an essential structural part linking the bridge with the ground, and its function is to transmit the loads smoothly from piers and abutments to the supporting strata. Unlike foundations of other civil structures, the foundations of bridges are subjected to dynamic loads coming from the superstructures, usually located in water or even deep water and torrents, and have large volumes and self-weights. Consequently, there are special issues related to the design, construction, and maintenance of bridge foundations need to be addressed, especially those relevant to the bridges crossing wide rivers, deep seawaters, and poor geological terrains. Based on the published journal articles and reports, this paper reviews the progresses in the research and development of bridge foundation types, foundation scour, foundation construction, and seismic resistance of foundations. Existing issues in the research and development of bridge foundations are discussed and, based on the discussion, the following topics are suggested for future studies: water-sediment interaction theory and mechanisms of sediment transport for scour at deep water foundations; advanced deep-water foundation structures suitable for China’s sea bedrock; key techniques for positioning and setting of large caisson foundations; and dynamic soil-foundation-structure interaction under earthquake.
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State-of-the-art review of concrete bridges and its high performance materials in 2020

Zhao Renda, Zhan Yulin, Xu Tengfei, Li Fuhai, Zhao Chenggong, Zhang Jianxin, Yang Shiyu, Yuan Yuan, Wen Xi

Abstract: (127) HTML (0) PDF (0.00 ByteKB) (0)

In order to understand the development trend of the research direction of concrete bridge and high-performance materials in 2020, and on the basis of summarizing the research contents, methods and achievements, the follow-up research will be carried out better, this paper reviews the recent literatures from the three aspects of concrete bridges, high-performance concrete materials and high-performance reinforced materials. Furthermore, the literature are classified, summarized and commented. The results show that the current research on concrete bridges pays more attention to durability in the operation stage, working performance in extreme environments, and concrete bridge accidents. For high-performance concrete materials, great progress has been made in the three aspects of high performance, green environmental protection and intelligence. The related high-performance reinforced materials have been mainly focused on the FRP bars with higher strength and better durability. Its application in beams, slabs, columns and other components has been widely studied. Finally, the paper points out shortcomings of the existing research and the work to be done in the future.
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State-of-the-art review of hydrology for bridges and culverts in 2020

Zhang Ming Jin

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Hydrology for bridges and culverts is mainly based on the river and hydrological environment and other factors for bridge design, which is an important basic work of bridge site environmental design. By reviewing the development of hydrology for bridges and culverts in recent years, some key issues from hydrology of bridges and culverts, such as research methods, design flood discharge, causes of bridge foundation scour and influencing factors, and calculation of the scour depth of bridge piers and abutments, elaborated the development achievements of hydrology for bridges and culverts and briefly summarized the current difficulties and future hotspots.
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State-of-the-art review of BIM Technology in Bridge Engineering in 2020

ZHAO Bin, XIE Shangying, HE Wei

Abstract: (238) HTML (0) PDF (0.00 ByteKB) (0)

Building information modeling is regarded as the second revolution of engineering design after CAD, is the key to digital transformation of civil Engineering Industry. But the application in bridge engineering is still rare, and research and application still need to be strengthened. In order to provide some references and new ideas for the future development of BIM in bridge engineering, this paper reviews, summarizes the research and application progress of bridge engineering BIM in 2020 from the following three aspects: (1) industrial policy, standards and guide, (2) basic research and software development, (3) application in bridge engineering.
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State-of-the-art review of bridge hydrodynamics in 2020

weikai, qinshunquan, zhaowenyu, zhubing, xuguoji

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To understand the development trend of the research of bridge hydrodynamics and on the basis of summarizing its research contents, methods and achievements, the follow-up research will be carried out better, this paper reviews the recent literatures published in 2020 from the aspects of wave current effect, local scour of foundation, fluid solid coupling, multi disaster effect of extreme marine environment, etc. It is found that the research hotspots of bridge hydrodynamics mainly focus on the models of an extreme wave, current action, and wave-current interaction, the influence factors and depth prediction of pier local scour, the fluid-structure coupling of the deep-water bridge under earthquake action, the combined effort of wind and wave Disaster assessment and risk analysis of bridge in an extreme marine environment, response analysis and optimization design of long-span floating bridge structure. By combing the shortcomings of the existing research, the following urgent research directions are proposed: structural fluid-structure coupling in extreme wave and current environment, pier erosion monitoring and protection, intelligent and information-based bridge hydrodynamic disaster prediction, and multi disaster research. It is expected to make joint efforts with relevant scholars to contribute to the development of bridge hydrodynamics.
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State-of-the-art review of bridge wind engineering at 2020

Haili Liao, Mingshui Li, Cunming Ma, Qi Wang, Yanguo Sun, Qiang Zhou

Abstract: (157) HTML (0) PDF (0.00 ByteKB) (0)

With the construction of super-long span bridges, such as the Canakkale 1915 Bridge in Turkey, the Zhanggao River-crossing Corridor and the Xihoumen Highway-Railway Bridge in China, the wind engineering research of bridges is facing new challenges. Following the research progress of the previous year, this paper focuses on the key problems of bridge wind engineering, including bridge flutter, vortex-induced vibration and buffeting. Through sorting out the literatures of main academic journals in the field of wind engineering, the state-of-the-art focusing on the main aspects of wind-resistant of long-span bridges in 2020 was reviewed and discussed.
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State-of-the-art Review of Big Data on Bridge Engineering in 2020

Yu Chuanjin, Chen Qian, Liang Aixia, He Jiayong

Abstract: (120) HTML (0) PDF (0.00 ByteKB) (0)

Under the background of the information era, the application of big data on bridge engineering has become a hot topic. The massive data obtained from data collection methods like bridge health monitoring have brought great challenges to bridge engineering practitioners in terms of data processing and application. Focusing on the research progress of big data on bridge engineering in 2020, this article reviews data preprocessing methods such as efficient storage, exception handling, redundancy and noise reduction, and focuses on specific applications of big data such as damage identification, condition assessment, and intelligent management. The relevant research progress of big data on bridge engineering in 2020 is sorted out and the existing achievements along with the focuses and difficulties of future research applications are summarized.
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Progress in construction technology of deep-water long-span bridges in 2020

Liu Junling, Yang Hanbin, Yang Wanli, Zhang Yuzhi

Abstract: (508) HTML (0) PDF (0.00 ByteKB) (0)

With the increasement of economic strength and significant improvement in science and technology, bridge engineering is developing rapidly towards larger span, deeper foundation and higher tower. Many new problems appears to bridge builders, such as: accurate positioning of deep water foundation during floating and sinking, anti-erosion of super-large caisson foundation, large diameter drilled pier construction, optimization of anchoring structure in long-span cable-stayed bridge tower, temperature control of hydration heat for mass concrete of ultrahigh bridge tower, development of new hydraulic climbing template system for ultrahigh bridge tower. These are the key problems for safe and smooth construction and long-term reliable operation for deep-water long-span bridges. The development and achievements gained in 2020 related to those key problems are analyzed and summarized to improve the construction technology, the problem-solving capacity of the builders and to give technical support for the promotion of deep-water long-span bridges.
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State-of-the-art review of the technology in bridge structure test in 2020

PU Qianhui, XU Xikun, WU Yining, HUANG Shengqian, HONG Yu

Abstract: (253) HTML (0) PDF (0.00 ByteKB) (0)

The bridge structure test is mainly a means to obtain the behavior of the bridge structure by applying static or dynamic action on the prototype or model of the bridge structure and using measuring and test techniques to collect precise and reliable test data, so as to solve the problems existed in scientific research and design in the field of bridge engineering. As an important means to promote the development of the bridge engineering field, the bridge structure test has been playing an important role for a long time. In recent years, with the progress of measuring and test technology, the technology in bridge structure test has also been widely concerned by scholars. In order to promote the further development of this field and guide the popularization and application of advanced measuring and test techniques in the field of bridge structure test, this paper systematically introduces the technical methods of three critical aspects: bridge model test, bridge field test and measuring and test technology of bridge, and reports and summarizes the enlightening related research in 2020. Finally, it is found that the technology in bridge structure test is further developing towards the integration of multi-disciplines.
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State-of-the-art review of cloud computing for bridge engineering in 2020

Yang Xingwang

Abstract: (243) HTML (0) PDF (0.00 ByteKB) (0)

Further development of bridge construction, integration of bridge design – construction – maintenance, refined management of bridge operation in China put forward higher requirements for data storage, computing capacity, etc. Cloud computing is an effective measure to satisfy the demands. By means of literature retrieval, cloud computing applications in bridge engineering in recent years are summarized, including bridge health monitoring (SHM), big data and internet of things in the bridge, BIM and collaborative design based on cloud computing. The feasible focuses of future research and application are suggested.
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State-of-the-art Review of Reliability in Bridge Engineering in 2020

Bin Wang, Ganggui Tang, Jishun Tang, Weixu Wang

Abstract: (205) HTML (0) PDF (0.00 ByteKB) (0)

Due to the uncertainty of the inherent properties and the complexity of the environment, bridges need to have sufficient reliability in different stages of design, construction, and operation. In order to understand the latest developments in the research and application of bridge engineering reliability in 2020, the relevant theoretical methods, scientific research content and results at different stages are summarized through literature review. In terms of the bridge reliability theory and methods, GPR models and radial basis neural networks are introduced to obtain the implicit structural function functions. Copula theory is introduced to consider the relationship between the probability of multiple failure modes. The probabilistic reliability and non-probabilistic reliability Methods, Monte Carlo simulation, time-varying reliability theory, etc. are used for reliability evaluation. The technical status and reliability of existing bridges are still hot spots in the field of bridge engineering at home and abroad. The time-varying model of bridge resistance and external load under environmental conditions is the focus of the time-varying reliability analysis and the life prediction of bridges. Reliability theory and analysis methods have been gradually developed in bridge engineering design. There are more and more dynamic reliability studies and applications that consider the randomness of dynamic load action and the randomness of structural parameters.
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New progress and prospect of bridge impact research in 2020

liuzhanhui

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Bridge impact is a key problem for existing bridges and bridges under construction for a long time. The research on impact and protection problems meets the needs of national development. In recent years, scholars at home and abroad have paid more and more attention to bridge impact, and conducted a lot of researches. Following the New Progress and Prospect of Bridge Impact Research in 2019, the author continues to summarize the progress in 2020 in three aspects, such as bridge ship collision, rockfall impact and vehicle collision bridge. Among them, for the bridge ship collision problem, the new code clearly proposes that the main structure of highway bridge should adopt the performance-based anti-collision design method. In 2020, a series of sand mining vessel collision accidents, the broken of Yaxi high-speed bridge, and many vehicle bridge collision events have occurred. The author sortes these bridge impact events, analyzes and summarizes the relevant achievements in the past year according to personal understanding, and then puts forward the problems that need to be further considered in the future research.
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State-of-the-art review of bridge informatization and intelligent bridge in 2020

Zhao Tianqi, Gou Hongye, Chen Xuanying, Li Wenhao, Liang Hao, Chen Zihao, Zhou Siqing

Abstract: (871) HTML (0) PDF (0.00 ByteKB) (0)

With the advent of digital era characterized by informatization and intelligence, the development and innovation of bridge engineering technology are promoted. It is necessary to integrate cloud computing, big data, artificial intelligence, 3D printing, robot and other strategic emerging industrial technologies with bridge engineering, and promote the industrialization, digitization and intelligent upgrading of bridges from multiple dimensions such as intelligent design, construction, operation and maintenance. This paper reviews related frontier technologies and important achievements worldwide in 2020, with regard to bridge informatization, intelligent inspection, safety operation and maintenance, intelligent disaster prevention/mitigation, intelligent materials, and summarizes the research hotspots and prospects. According to the review, BIM technologies can improve the refinement of bridge forward design, the accuracy of construction process control and management. Intelligent inspection technologies (e.g. UAV and robots) and artificial intelligence technologies (e.g. machine learning and convolution neural network) improve the accuracy and efficiency of bridge inspection and monitoring. Applications of high-performance intelligent materials promotes the self-perception, self-adaptability, self-adjustment and self-diagnosis of bridge. Natural disaster monitoring and early warning based on artificial intelligence (AI) provides new development idea for bridge intelligent disaster prevention. To conform to the development trend of informatization and intelligence, future research should deeply integrate artificial intelligence technology into the whole life cycle of bridge design, construction and maintenance to realize the dream of bridge power.
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State-of-the-art Review of Risk Assessment on Bridges Construction in 2020

Shi Zhou, Yu Wangqing, Zhou Yongcong, Ji Feng, Zhang Yuzhi

Abstract: (166) HTML (0) PDF (0.00 ByteKB) (0)

To understand the specific contents of bridge construction risk assessment and the development trend in the past year, and to carry out the better follow-up research on the basis of summarizing the research content, methods and achievements, the recent literatures were consulted, classified, summarized and commented from four aspects of the bridge construction risk identification, risk probability and loss estimation, risk assessment and control, dynamic risk assessment. The results show that the composite risk identification method, risk identification database system and visualization were developing continuously. The quantitative probability correction based on monitoring data and the construction of social loss model were the new development of risk probability and loss estimation. The new development of risk assessment was based on clustering or data field risk assessment method and the improvement of model accuracy. The fine modification of risk chain transferring model and dynamic evaluation model based on monitoring data were the new directions of dynamic risk assessment. Finally, some suggestions were put forward for the shortcomings of the existing research and the further development of this direction, which can be references for the work to be done in the future.
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New Research Progress on Bridge Aesthetics in 2020

Yan Liang, He Wei, Maolin Tang

Abstract: (224) HTML (0) PDF (0.00 ByteKB) (0)

This article sorts out the domestic and foreign development of bridge aesthetics in recent one year to review the development achievements by some aspects such as bridge aesthetic thought and theory, bridge aesthetic design methods and theory, bridge landscape design and reconstruction, bridge planning and design, bridge design and research on culture and history, new technology application on bridge aesthetic design, bridge aesthetic design and practice etc. Brief prediction of future research hotspots and development directions are made and the author"s suggestions and viewpoints are put forward in the end, hoping to be benefit with bridge aesthetics theory and design practice.
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State-of-the art review of box girder and cable-supported bridge analysis theories in 2020

BAI Lunhua, SHEN Ruili, MIAO Rusong, ZHANG Xinbiao, WANG Lu

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Modern bridges is symbolled by long-span, light-weight and high-strength, of which the box girder and cable-supported bridges are two important parts. To that point, the corresponding research progress in 2019 of the related theories is summarized by the authors^[1], including the theory of the new box girder with corrugated steel webs and traditional box girder, the interaction between cable and saddle in multi-tower cable bridge, the ultimate load capacity of cable-supported bridges, and application of UHPC technology in cable-supported bridges. A review is made to further understand the research trends of the above five aspects in 2020. In addition, the recent development of the cable-supported bridges is discussed. It is concluded that as the emergency of the new structural forms the refined analysis theory of box girder and cable-supported bridges have new opportunities to extend.
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State-of-the-art review of bridge maintenance in 2020

lijun, Wei Xing, Tang Chaoyong, Zhang Bolun

Abstract: (265) HTML (0) PDF (0.00 ByteKB) (0)

The purpose of bridge maintenance is to maintain the normal traffic function of the bridge, to meet the requirements of load,speed and other factors, and to prevent sudden and serious disasters. Bridge maintenance has the characteristics of long-term, local and emergency. At present, there are special bridge maintenance institutions at home and abroad, which have formed systems and specifications for daily inspection, regular inspection, special inspection, special inspection, maintenance and reinforcement of bridges. The maintenance contents and key points have been clearly defined and implemented, and the maintenance technology can meet most of the requirements. At present, the outstanding problem is how to achieve rapid maintenance and emergency treatment. High speed railway and urban rail transit are in uninterrupted operation, high-density traffic, and construction is prohibited during traffic. They can only use the skylight time of 0-4 a.m. every day for maintenance, and the line must be opened after 4 a.m. every day. Highway also requires continuous maintenance. After the occurrence of sudden disasters, it needs emergency treatment and maintenance. The maintenance system of railway system makes it easier to collect data and realize data standardization. Bridge maintenance is developing in the direction of rapid maintenance and intelligent maintenance. This paper mainly introduces the research progress of bridge maintenance in 2020 from three aspects: disease and treatment, maintenance strategy and new maintenance technology.
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Research progress in 2020 of the application of fiber reinforced polymer in bridge structures reinforcement

Ye Huawen, Tang Shiqing, Duan Zhichao, Liu Jilin, Yang Junchuan

Abstract: (507) HTML (0) PDF (0.00 ByteKB) (0)

Fiber-reinforced polymer(FRP) has been widely used in modern bridge engineering and old bridges reinforcement in recent years due to the excellent material properties that can adapt to the development needs of bridge structures towards light weight and durability. In order to promote the development of bridges structures reinforcement using composite materials as well as meet the diversified needs of engineering operation and maintenance, this article reviews the research on the reinforcement characteristics of old bridges, the performance of FRP and the methods of strengthening bridges. The research and application of FRP in bridges reinforcement in recent years is elaborated in detail from two aspects of concrete and steel bridge reinforcement. FRP has become an important bridge reinforcement method because of its obvious strengthening performance and great efficiency. In order to develop and expand its application scope, it is necessary to standardize FRP anchor, promote the monitorability of strengthened bridges and establish a specification system of FRP strengthened bridge structures.
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State-of-the-art review of seismic design of bridge in 2020

Zhao Canhui, Jia Hongyu, Yue Weiqin, You Gang, Jia Kang, Zheng Shixiong

Abstract: (237) HTML (0) PDF (0.00 ByteKB) (0)

Earthquake may cause great damage to bridge structure, damage and even collapse of bridge. The seismic resistance of bridges has always been an important research direction in the field of bridges. This paper summarizes the research results and development trend of the seismic field of bridges in 2020, and the main conclusions are as follows: the seismic performance of the pier column after replacing ordinary concrete with new materials is explored; The shaking isolation pier has good seismic performance through shaking table experiment and numerical simulation; The displacement ductility and residual displacement of the pier can be improved by using the carbon fiber cloth sheath to strengthen the pier column; The traditional single leg to double limb thin-walled high pier has better seismic performance, the hysteretic curve of the double limb thin-walled pier with high main reinforcement ratio is full, and the energy consumption performance is good, and the axial pressure ratio is improved significantly; The rectangular hollow double column high pier with energy dissipation beam has better energy consumption capacity, bearing capacity and displacement ductility; The system of vibration reduction with friction pendulum support and limit energy dissipation rod has good effect of reducing isolation, and the internal force damping rate can reach more than 20%; The reliability of using new type of unbonded steel mesh rubber support (USRB) instead of unbonded laminated rubber support (ULNR) in bridge is studied; The influence of near field vibration and soil structure interaction on the dynamic response of the bridge is investigated.
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Test research on corroded RC beams under the influence of different strengthening schemes using steel plate

Tang Huang, Peng Jianxin, Wang Han

Abstract: (277) HTML (0) PDF (0.00 ByteKB) (0)

In order to explore the influence of different strengthening schemes using steel plate on the bearing capacity of corroded RC beams, and the strengthening effect of different strengthening schemes are explored. The characteristics in the bearing capacity, deformation, failure mode and ductility of corroded RC beams strengthening by steel plate with flexural strengthening schemes, shear strengthening scheme and flexure-shear combination strengthening scheme are compared, and the advantages and disadvantages of different strengthening schemes are analyzed. The results show that: for the flexure-strengthened corroded beam which steel plate thickness are 3mm, 4mm and 5mm, respectively, the ultimate bearing capacity of flexural strengthened corroded beams increases by 7-18kN with the increase of steel plate thickness. The effect of combined strengthening is most obvious, and the ultimate bearing capacity increases by 107.7% compared with corroded beams. Combined strengthened corroded beams have the strongest deformation resistance, the followed is flexure-strengthened corroded beams, the increase of steel plate thickness has a positive effect on the deformation resistance of flexure-strengthened corroded beam. The combined strengthening scheme can most effectively improve the ductility of corroded beam than the other two strengthening schemes, the ductility of which is improved by 320.4% compared with corroded beam, followed by shear strengthened corroded beams. The ductility of flexure-strengthened corroded beam is smaller than that of other two kinds of strengthened beams, and which increases first and then decreases with the increase of steel plate thickness. The deformation resistance and ductility should be considered comprehensively when evaluating the strengthening effect of flexure and shear strengthened corroded beams.
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Analysis of normal section bending bearing capacity of inverted U-Shaped steel-encased concrete composite beam

yanqiwu, zhangzheng

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In order to study the normal section bending capacity and structural requirements of a new type of inverted U-shaped steel-encased concrete composite beam, nonlinear finite element models of the composite continuous beams have been stablished with the reference of the existing U-shaped steel-encased concrete composite continuous test beams, and the load-mid-span deflection curves of the finite element models of the composite continuous beams have been simulated and compared with the related test results. The rationality and effectiveness of the modeling method and parameter selection of the composite beam finite element models are verified. Based on the finite element model of composite continuous beams, the main influencing parameters of bending capacity of inverted steel-encased concrete composite beams are analyzed. Based on the test and simulation results of normal section bending capacity of inverted U-shaped steel-encased concrete composite continuous beams, a simplified plastic theory is proposed to calculate the normal section bending capacity of composite beam, but the plastic theoretical calculation value of the normal section bending capacity of the composite beam should be multiplied by the modified coefficient of 0.96. The comparison between the plastic theoretical calculation value of the normal section bending capacity of the composite beam and the simulation value of the finite element model of the composite beam shows that the two values are very safe and close, and the modified simplified plastic theory calculation value of the normal section bending capacity of the composite beam is accurate and reliable enough.
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Engineering test and numerical analysis of underground concrete silo

JIN Libing, Liang Xinya, Huo Chengding, Wang Zhenqing, Wang Zhen

Abstract: (469) HTML (0) PDF (0.00 ByteKB) (0)

The underground granary can take full advantage of the underground space, it has better fireproof, anti-toxicity, explosion-proof and other properties. In the meantime, the underground silo can use the shallow geothermal energy to realize quasi-low temperature storage. With the advantages of energy-saving, low-consumption and grain quality-ensuring, it plays a significant role in ensuring the grain safety and sustainable development of China. This paper adopted the combination of engineering full-scale test and numerical analysis to carry out engineering tests at different construction stages of the large underground concrete silo, and conducted engineering tests and numerical simulation on the mechanical properties of the silo wall at different construction stages to verify the rationality and validity of the numerical analysis method. Furthermore, the mechanical properties of the wall of the most unfavorable working conditions under the combined soil and water pressure were numerically analyzed. The results show that the internal forces of the numerical simulation results of the silo wall were in good agreement with the experimental results, which verified the validity of the numerical method, the radial stress of the silo wall was highest at the bottom of the silo wall, and the hoop stress was highest at about two-thirds of the top of the silo wall. This method can provide reference for the mechanical analysis and structural design of similar underground reinforced structures.
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Study on Vertical Uplift Resistance of the Foundation of Plate and Ball Connected by Anchor Cable

wangxuejiao, yanzhixin, longzhe

Abstract: (426) HTML (0) PDF (0.00 ByteKB) (0)

In the light of the engineering characteristics of sandy soil foundation in desert area and the shortcomings of existing transmission tower foundation, a foundation of plate and ball connected by anchor cable is developed. This foundation not only fills the gap of transmission tower foundation in desert area, overcomes the construction difficulties of sandy soil foundation, but also meets the requirements of safety and stability of the project. By means of the combination of the similar model uplift test and numerical simulation, the displacement of foundation under different uplift loads is analyzed. And, the effects and the law of influence of buried depth ratio, spherical diameter and column diameter on the ultimate uplift bearing capacity coefficient of foundation and the radius of main rupture surface of soil surface are studied. The results show that the numerical simulation results are in good agreement with the model test results, and the load-displacement curve presents a three-stage change, which corresponds to the three stages of soil deformation evolution. The ratio of buried depth has the greatest influence on the ultimate uplift resistance of foundation, and there is a positive correlation between them. The ultimate uplift bearing capacity coefficient increases first and then decreases with the increase of burial depth ratio, and is negatively correlated with sphere diameter and positively correlated with cement-soil column diameter. The radius of main rupture surface of soil is negatively correlated with the buried depth ratio, spherical diameter and column diameter.
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State art of biogeotechnology and its engineering implications

huyingkui

Abstract: (579) HTML (0) PDF (0.00 ByteKB) (0)

This paper summarizes biochemical reaction processes and mechanisms of the major microorganisms involved in the field of bio-geotechnical engineering. The researches focus on soil improvement technology, sealing technology, contaminated soil remediation technology are summarized and discussed. Through the collection and summary works on this topic, this paper aim to promote a deeper and more comprehensive fundamental researches and contribute to promotion and application of the bio-technology in geotechnical engineering.
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Experimental study on the shear behavior of fiber-reinforced bio-cemented sand

Zheng Junjie, Song Yang, Lai Hanjiang, Cui Mingjuan, Wu Chaochuan

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Microbial-induced calcite precipitation (MICP) has the prominent advantage of significant improving the shear strength of soil,while MICP sand also has the obvious shortcoming of brittle failure． A certain amount of fiber was added into MICP sand in order to improve the brittleness,and based on consolidated drained triaxial compression tests,the shear strength characteristics of fiber-reinforced bio-cemented sand was studied．And then,the effects of fiber content,fiber length and initial relative compactness of samples on the shear characteristics of fiber-reinforced bio-cemented sand were discussed．Finally,the corresponding mechanisms of strength enhancement and ductility improvement were also investigated through scanning electron microscope．The results show that during the process of MICP,calcium carbonate crystals deposited on the fiber surface effectively improve the roughness of fibers surface,while the mixture of calcium carbonate and sand provides anchorage to the fibers,enhancing the shear strength of MICP sand and improving the strain softening characteristic,and it is concluded that fiber has the potential to improve brittleness of MICP sand．
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Study on Removal of Compound Pollutants in Water by Coagulation - Ultrafiltration Process

Zhaochun, Jinfan, Anye, Sunzhihua, Zhenghuaili

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The effect of humic acid (HA) on the stability of nano-TiO2 was analyzed, and the effects of coagulant dosage, pH and calcium(Ⅱ) concentration on the removal efficiency of HA- TiO2 composite pollutants by the coagulation-ultrafiltration process were investigated. The results showed that the electrostatic adsorption and coordination reaction occurred between nano-TiO2 and HA in the aqueous solution, which caused the decrease of effective particle size of nano-TiO2, the enhancement of electrostatic repulsion, more uniform dispersion of colloid, the increase of system stability and easy migration. These posed a threat to the safety of drinking water. The optimum parameter for HA-TiO2 composite pollutants removal was that the coagulant concentration is 0.46 mmol/L, and the initial pH value is between 7 and 8. The calcium ion in the solution will lead to the decrease of membrane filtration flux and increase the membrane fouling.
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Study on heat conduction of fire protection for isolated rubber bearings under fire

Wang Lan, Wang Lixiong, Zhan Wangyu

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This paper studies the heat conduction limit of fire protection for isolated rubber, and provides theoretical evidence and experimental data for fire protection. Based on one-dimensional unsteady heat conduction, formula under ISO834 standard fire is derived. According to the GB9978.1-2008 fire test, three kinds of components, LNR500, LNR1500 support board fire protection, LNR500 support board with flexible fireproof material fire protection, are tested.Modeling and finite element thermal analysis are carried out on ABAQUS. The numerical analysis and fire test results verified our theory. Based on the derivation and experiment data, when the temperature of the support surface reaches the critical temperature 150 C, the table of the limit thermal conductivity of fireproofing board with different thickness can be referred in engineering applications.
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Vibration testing and comfort evaluation of floorslabs under pedestrian and escalator loads

PAN Yi, WANG Shuangxu, GUO Rui, HU Wenhao

Abstract: (279) HTML (0) PDF (0.00 ByteKB) (0)

On lap escalator cantilever floor under pedestrians - escalator coupling is prone to lead the problem of vertical vibration, in a commercial laminated cantilever in the floor as the background, take the field vibration test method, the escalator running, the number of pedestrians and pedestrian movement on the influence of the cantilever floor vibration response, and through the test data of floor structure vibration comfort perception evaluation and personnel. The results show that the movement of pedestrian on escalator is the main reason for the vibration of overhanging roof. The vibration of the roof is more obvious in response to the increase of the number of people accompanying it, but decreases with the increase of the length of the escalator. The peak acceleration was used to evaluate the comfort of overhanging roof, and the vibration response of overhanging roof exceeded the comfort limit when pedestrians ran on the escalator. Use KB (Konstant Beurteilungswerte) value to judge the perception of cantilever floor, when the pedestrian relatively static escalators, the vibration of the cantilever floor not beyond the permissible value perception degrees, when pedestrians are relatively escalator when walking or running, the vibration of the cantilever floor would be beyond the permissible value perception degrees; The movement of people relative to escalators does not cause the overhanging roof to resonate.
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Study on preparation and performance of anti-blocking pervious concrete

Tang Jing, Zhao Yuting, Liang Meikun, He Binwei, Yu Yiheng, Zeng Lu

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In order to improve the permeable performance of pavement, polymer pervious concrete has been widely used in the construction of sponge city. Special fine sand and epoxy resin were used to prepare permeable materials. The influence of particle size and polymer dosage on the compressive strength and permeable coefficient of permeable concrete were discussed by controlling variable method. At the same time, the simulation experiment of blockage was carried out. Based on the image analysis of the aperture of the permeable concrete, and the properties of the concrete was analyzed by observing the microstructure of the concrete. The experimental results show that with the same particle size, with the increase of epoxy resin content, the compressive strength of the permeable concrete gradually increases, while the water permeability coefficient decreases gradually, When the particle size of aggregate is 0.15-0.3 mm, the compressive strength of permeable concrete appears to increase initialy and then decrease, while the permeable coefficient appears to increase continuously. When the aggregate particle size is 0.15-0 .3 mm and the epoxy resin is 5 % of the aggregate mass, the average porosity of the permeable concrete is 14 %, and the average equivalent diameter is 214um. The aggregate blending ratios with particle sizes of 0.15-0.3 and 0.3-0.6 were 1:1, with a compressive strength of 41.7MPa and a permeation coefficient of 1.7mm/s, showing best performance. After the product blocks four cycles, the permeability attenuation coefficient is less than 20%, and the anti-blockage performance is great.
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Modal analysis and experimental study of spoke cable-trusses

WANG ZE QIANG

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Through the modal analysis and test of the 1:10 scale model of 60m circular spoke cable-trusses, the influence of 3 parameters of cable prestress, rise to span ratio and diameter ratio of inner and outer ring on the natural vibration characteristics of the structure were investigated. The results of test and theoretical of the first four order modal were compared and analyzed. It can be seen that: The first, second order vibration modes of the structure are antisymmetric upper and lower vibrations, the third order is the inner ring torsional vibration, and the fourth order is the relative torsional vibration of the inner ring. The frequency error is less than 10%, and the experimental mode of vibration is in agreement with the theoretical mode. The frequencies of the first four modes are all above 10Hz, indicating that the spoke cable truss structure is of low frequency dynamic response, and the natural frequency is small and the distribution is dense. When prestress level of the structure is higher, the modal frequency will increase, and the stiffness will also increase. With the increase of sagittal height, the structural frequency will decrease, and the structure is more prone to lateral instability. With the increase of the inner and outer ring diameter ratio, the torsion stiffness of structure will decrease and torsion instability will also occur.
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Bond Behaviour Study on Interface between Steel Plate and Bonded Concrete under Hydrothermal Environment

yaoguowen, liuyusen, wutianyu, lishiya

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The interface performance between steel plate and concrete is the key to strengthened concrete structure. In this paper, there were 27 specimens carried out for steel plate bonded concrete under hydrothermal environment. And accelerated hydrothermal aging was respectively conducted in 5 days, 10 days and 15 days. Then the double- shear test was performed to obtain the ultimate load, strain distribution and relationship of load-displacement during the shear failure process on steel plate-concrete interface. After long term temperature and humidity coupling, the durability of the steel plate-concrete interface was studied. Considering the analysis of bond failure mode, loading process and the relative displacement evolution on bonding interface, the expression of shear stress and slip was proposed, which was related to temperature and humidity. Finally, the bond-slip constitutive model was established in consideration of the temperature and humidity. The numerical simulation results were in good agreement with the experimental results. The results of the paper provide reference for the design of the concrete structure with bonded steel plate and the durability theory.
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Validation and Revision of Two-node Model in Outdoor Unsteady Environment in Hot and Humid Region

Jiang Yi, Zhao Lihua, Meng Qinglin, Mochida Akashi

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Because of rapid urbanization and global warming, urban outdoor thermal discomfort and risk of thermal safety increased. In order to find out the physiological parameters changes of human body in outdoor thermal environment, provide a basis for rapid urban thermal environment evaluation, carried out the human thermal response measurement, then analyzed the simulation accuracy and coincidence degree of the two node model, found out that changes of environment which human in and human activity on human physiological parameters. Based on set-point of skin temperature and core temperature, standard human model, temperature of regulation starting, convective heat transfer coefficient, the two-node model was verified and revised, and a new two-node model for predicting outdoor human thermal response was developed.
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Experimental Study On Effect of Inlet and Outlet Water Temperature On Performance of A Large Temperature Difference Bathing Wastewater Source Heat Pump Unit

Ma Liangdong

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Bathing wastewater contains a large amount of waste heat. A large temperature difference heat pump unit was proposed to maximize the recovery of heat energy from bathing wastewater by the authors. The rated design conditions of the unit are: the entry and exit temperatures of evaporator side bath wastewater are 30℃ and 6℃, respectively. The inlet temperature of tap water on the side of the condenser is 5℃, the outlet temperature of hot water is 45℃, and the theoretical calculation value of the maximum coefficient of heating performance (COP) is 4.9. In this paper, the effects of inlet temperature of tap water, outlet temperature of hot water and inlet temperature of bath wastewater on thermal performance of heat pump unit were studied experimentally. The experimental results show that the COP of the whole unit is 5.0 under the rated design conditions. When the inlet temperature of tap water increases from 5℃ to 15℃, the overall unit COP was reduced from 5.0 to 3.85. But if the inlet temperature of tap water is less than 10℃, the overall unit COP is higher than 4.5; When the temperature of the hot water outlet changes from 40℃ to 50℃, the overall unit COP gradually decreases from 5.3 to 4.9. And when the inlet temperature of bath waste water rises from 30℃ to 35℃, the overall unit COP rises from 4.8 to 4.95.
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Tensile test of pultruded GFRP pipe connected with steel pipe

Zhu Mingqiao, Li Zhibin, wangyao

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Abstract: The reliable connection of pultrusion forming GFRP pipe joints is a prerequisite to ensure the normal operation of the components. In order to research its tensile connection performance, this paper adopts two kinds of connection modes of bonding connection and bolt connection in GFRP pipe and steel pipe connector, and carries out its tensile test research respectively. The distribution characteristics, force mechanism, failure process and the influence of bonding length on load-bearing capacity of glue layer shear stress along the length direction was studied in the adhesive bonding test. The experimental results show that the shear stress of the glue layer is large at both ends and small in the middle along the length direction at the initial stage of loading. As the load increased, the stress gradually shifted towards the loading end of the glue layer. The increase of bonding length can significantly improve the load-bearing capacity of the connecting parts, but when the length reaches 1.6 times of the pipe diameter, the increase of the bonding length is not obvious to the increase of the load-bearing capacity. Therefore, the 1.6 times the pipe diameter can take into account as the effective bond length of the GFRP pipe. The influence of e/d (edge distance/bolt diameter) and bolt row number on the connection load-bearing capacity and failure mode were studied in the bolt connection experiment. The experiment results show that when is equal to 7, the load-bearing capacity reaches the maximum value and the main failure mode is extrusion failure. According to the relationship between the bolt row number and the load-bearing capacity, the corresponding reduction coefficient can be deduced for calculating the load-bearing capacity.
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Research on active failure and earth pressure of cohesionless soil with limited width behind retaining wall based on DEM

wanli, zhang xingzhou, WANG Yufeng, XU Liming, XU Changjie

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The classical Coulomb and Rankine earth pressure theories are based on the assumption that the soils near a retaining wall are semi-infinite. It is obviously that these theories are no longer suitable for the narrow backfill behind a retaining wall. A series of numerical simulation are conducted with DEM to study the active failure process of limited cohesionless soil behind a rough or smooth wall. The development of the failure surface, the displacement field of the soils and the distribution of active earth pressure are analyzed. The results obtained from DEM show that multiple slip surfaces occur in the backfill if the soil behind the smooth wall is narrow enough. The slip surface angle is close to the Coulomb’s theoretical solution, which shows no related to the width height ratio. This ratio also has little influence on the active earth pressure in this case. In another case, when the wall is rough, the actual shape of failure surface is a curve rather than a straight line. The rougher the wall, the weaker the reflection. The angle of failure surface decreases along with the width height ratio of soils increases. And the failure surface is finally located inside the Coulomb’s failure surface. There exists a critical width height ratio of soils behind the rough wall. The active earth pressure decreases with the increases of the ratio if it is smaller than the critical ratio, but the active earth pressure is independent with the ratio if it is larger than the critical ratio. The smaller the width height ratio is, the smaller displacement of the ultimate equilibrium state will be, regardless of roughness of the retaining wall.
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Multi-parameter experimental study on reinforced concrete two-way slab with studs

JIN YU, YI WEIJIAN, HU LAN, MA KEJIAN

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The main objectives in this paper are to study mechanical performances of reinforced concrete two-way slab with different stud parameters.The experimental study on 7 reinforced concrete two-way slab-column connections with punching shear studs were completed.The main parameters were spacing of stud, the diameter of the stud, the height of the stud, the strength of the stud and the arrangement of the stud.The entire process of damage of slab-column connections with studs was simulated by using static loading method. By comparing and analyzing the test results of specimens with studs,the results show that increasing the diameter of the stud,the height of the stud or the strength of the stud can improve the anti-punching shear performance of the specimen.The increase in diameter is the most obvious, and the increase in deformation is 36%.Increasing stud spacing and reducing stud height are both not good for the improvement of the test, and the load-bearing capacity and the deformation are reduced.By comparing three different stud arrangements it is found that using radiation arrangement with the same number of studs and orthogonal arrangement with increasing the number of studs are both conducive to the improvement of the specimen anti-punching shear capacity,and the former was more economical.And then the reliability of the test results was verified by comparing the calculated results of relevant specifications with the test results.The results show that the safety reserve of specification calculation results of slab-column structure with studs is enough. However,it is not enough to reflect the nature of test results,especially contributions of the stud to anti-punching shear performance of slabs are underestimated.
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Analysis on end-bearing capacity and end-bearing resistance factor for piles socketed into rocks

Lu Xianlong, Qian Zengzhen, Yang Wenzhi, Zheng Weifeng

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It is an important issue to investigate the characteristics of end-bearing capacity and to determine the end-bearing resistance factor for the application of rock-socketed piles. In this study, the results of 165 compression load tests were collected to examine several issues related to the end-bearing capacity behavior of rock-socket piles. All these load test results were conducted on different rocks with different rock-socket piled conditions by different authors worldwide. Using these load test data, the type and the uniaxial compressive strength of rock in nature, the diameter and the embedment depth of socketed piles, the ultimate end-bearing resistances were compiled. The ratio of ultimate end-bearing capacity to unconfined compressive strength of the rock was defined as the end-bearing resistance factor of rock-socketed piles. Effects of the pile diameter, the pile depth rocked into rock, the ratio of rocketed depth to diameter, and the unconfined compressive strength of the rock on the ultimate end-bearing capacity and the end-bearing resistance factor were comprehensively investigated. An empirical relation between the unconfined compressive strength and the end-bearing capacity as well as the end-bearing resistance factor were suggested, which could be used in the design for rock-socketed piles.
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Multi-parameter Simulation Method of Semi-Rigid Node of Steel Tubular Scaffold with Couplers

Xie Xiangyang, Chen Guo, Yin Lei

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Upright tube’s 6 degrees-of-freedom are constrained by horizontal tube and diagonal brace at the coupler connection joint, the strength of such constrains is the key factor of the stable bearing capacity of the scaffold. To determine the efficiency of the constraints, single factor sensitivity analysis and eigenvalue buckling analysis methods are applied to measured each constraints’ contribution on stable bearing capacity. The efficiency analysis results of their contributions indicated the mechanism of constraints and then horizontal tubes and bracing tubes. Reasonable effectiveness of 6 constrains is tentativly researched according published experimental data of couplers, and then a multi-parameter simulation method of semi-rigid node is proposed. The premise condition of the multi-parameter simulation method is validated by the comparison between the experimental loads and the the inner forces’ calculating results of the couplers, in which effective length method and linear elastic second-order analysis method is adopted. Accompanying with the research of multi-parameter simulation method,some common deficiencies or limitations of ordinary methods which are based on single parameter assumption are listed and analyzed.
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Preparation of Multiwalled Carbon Nanotube/Cuprous Oxide Composite Microsphere and its Photocatalytic Property for N-formylmorpholine(NFM) wastewater

CHE Chun-bo, ZUO Jin-long

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Multiwalled carbon nanotubes/cuprous oxide (MWCNTs/Cu2O) composite microsphere was fabricated by liquid phase reducing method. The analysis of functional group, phase and morphology on the samples were characterized by IR, SEM and XRD. The results showed that MWCNTs were combined with Cu2O to form composite microsphere by vertical and horizontal interspersing. Compared with pure Cu2O, MWCNTs/Cu2O composite catalyst has more excellent catalytic effect for target organic N-formylmorpholine(NFM) wastewater.
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Optimization of Photopolymerization CMCTS-g-CPAM by Response Surface Methodology and Evaluation of Sludge Dewatering Performance

Zhu Hui, Sun Wenquan, SUN Yongjun, Zheng Huaili, Tang Mengdan

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Excess sludge, product of sewage treatment, is increasingly produced. Sludge decontamination is required before sludge disposal, and sludge conditioning is a very important step. Cationic sludge dehydrating agent of CMCTS-g-CPAM was synthesized using Carboxymethyl chitosan (CMCTS), acrylamide (AM) and methacryloyloxyethyltrimethylammonium chloride (DMC) as monomers, azobisisobutylphosphonium hydrochloride (V-50) as an initiator through initiating polymerization by ultraviolet light. The preparation conditions of CMCTS-g-CPAM sludge dehydrating agent were optimized by response surface methodology (RSM) taking the photoinitiator concentration, pH and illumination time as the object of investigation, the intrinsic viscosity of CMCTS-g-CPAM as the response value. The optimal illumination time, photoinitiator concentration, and pH of respectively 2h, 0.04% (volume fraction), and 9 were obtained by response surface analysis. FT-IR and 1H-NMR of the graft copolymer indicated that AM and DMC were successfully grafted to CMCTS. Finally, the synthesized product was applied to sludge dewatering. The experimental results showed that it has good sludge dewatering performance. Sludge specific resistance decreased to 1.96&#215;1013m/kg, and the moisture content of the filter cake decreased to 79.28%,at the flocculant dosage and pH of 30mg/L and 10, respectively.
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Dynamic performance of closed heat source tower in winter non – frosting conditions

jiayuhao, linianping, cuihaijiao, zhangnan

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In order to investigate the heat transfer process in closed heat source tower under the non-frosting condition, the finite difference method was adopted to develop the dynamic heat and mass transfer model. Comparing the calculated results with the experimental findings, the root mean square error of the outlet solution temperature is 0.201 °C. Through experiments and simulations, dynamic performance of the closed heat source tower during variable load operation are analyzed, results show that the closed heat source tower, as a heat source, can provide solution with relatively constant temperature for heat pump when working condition changed, in addition, compared with traditional air source heat pumps, the closed heat tower has lower frost risk in the low temperature and high humidity environment.
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TheSanalysisSof mechanical properties of multiple-structure thick overburden pervious foundation based on fluid-solid coupling

WANG Zheng-cheng, MAO Hai-tao, LONG Shun-jiang, JIANG Hai-bo, ZHANG Ru-yi

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The mechanical properties of every soil layer in multiple-structure thick overburden pervious foundation diverge significantly and specific problems that draw attention are diverse in range, which requires further study. This paper derived from the principle of Biot consolidation theory takes into account soil non-liner rheological and the change of porosity, permeability coefficient, elastic modulus and poisson ratio at the consolidation deformation process of soil. The coupling process of seepage and stress fields of Daga hydropower station dam foundation is simulated by fluid-structure interaction module of ADINA to analyze mechanical properties and interaction of each layer. The research shows that the looser permeable soil on surface is the main seepage channel, inlet and outlet area of seepage and settlement deformation reflects area, and measures should be taken to improve the compression modulus in upstream and install the anti filter layer and drainage facilities in downstream area. Fine sand layer in dam foundation is the main reason of dam foundation settlement, which plays a leading role in dam foundation settlement, at the same time, attention should be called to the liquefaction properties of adverse impact on the dam foundation. Artesian aquifer in dam foundation produce up-holding force on the downstream side of the upper structure, and the destruction is small if the location is deep. Deep soil layer have a less effect on seepage failure of dam foundation, but the effect can not be dismissed on settlement and seepage flow. Since in the permeability coefficient of sand gravel stratum and fine sand layer exists a modest distinction, the soil layer does not generate the contact erosion. In addition, the most of pore water pressure is dissipated at rapidly-declining phase, dam foundation shows a tendency of stability at rapid consolidation stage. Vertical cutoff wall can effectively decrease seepage gradient and seepage discharge, and the settlement deformation of dam foundation is controlled in upstream region of cuttoff wall. But the deformation of upstream dam foundation produce a large horizontal thrust to cutoff wall, so the size of cutoff wall should be increased or auxiliary seepage control measures adopted to contain that.
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Influence of Summer Dressing Behavior to Office Building Air-conditioning Energy Consumpution in Beijing-Tianjin Regions

lisha, Qian Xiaoming, Yang Ruiliang

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Dressing-behaviour affect building air-conditioning energy consumption by indoor air parameter. Energy consumption simulation software DEST is used , the energy consumption of operating and expectation parameter is lower 10.86% and 13.16% of the recommended standard parameter in Beijing-Tianjin regions. While it is lower only 4% to the experimental thermal property of typical dressing behavior.It stated the subjective temperature related with thermal resistance need amendment by the dressing behavior of region. The model of dressing behavior adjust office building Air-conditioning Energy Consumpution is given. Energy saving rate of dressing behavior isεc, Energy saving ifεc is negative,on the contrary there is no energy saving. The critical thermal resistance is 0.563clo when energy saving rate is 0 in Beijing-Tianjin Regions. The premise of energy saving is thermal resistance of dressing lower than The critical value in the design and operation of air-conditioning system. The model of dressing behavior offer quantitative criteria of style and fabric in region, supply a method to accuracy control energy consumption.
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Study on Safety Risk Assessment Method for Road Slope in Western Hubei Mountain Region

Luo Hongming

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The realistic needs of mountainous highway construction in China are explored and studied on risk problem, which is inevitably exist in the mountain highway construction, otherwise, safety risk assessment of mountainous highway slope has important theoretical and practical significance. Highway slope safety risk prediction and evaluation methods are established which based on geological hazard risk assessment methodology. Safety risk assessment for Taishangou tunnel entrance slope of Shiyan to Baihe highway is studied by risk evaluation method of geological hazard. Monte Carlo simulation is used to get the stability of the slope probability of failure under the conditions of normal operation and abnormal conditions. And the vulnerability for the part of slope within the affected areas is analyzed. Possible economic loss and population casualties are obtained through the risk calculation formula. The results show that: Taishangou tunnel entrance slope is less risk in the natural conditions under the conditions of the acceptable range class; but slope is higher risk in non-normal conditions, management measures must be taken to reduce risk and to strengthen monitoring, particularly to strengthen the monitoring of slope deformation in the construction process and adverse natural conditions. The result is provided guidance for slope protection and safe operation of Shiyan to Baihe highway.
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Volume 46,2024 Issue 2

土木工程

Environmental Engineering

Research Progress Report

Volume 46,2024 Issue 2

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