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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

Abstract: (415) HTML (0) PDF (2.31 MKB)(588)

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 of statistical damage constitutive model for rock considering pore ice

Long Haiping, Zhang Haoyang, Min Qinghua, Jiang Annan, Zheng Fu

Abstract: (48) HTML (0) PDF (0.00 ByteKB) (0)

Artificial freezing method has become a key construction technology for underground space engineering to cross the water-rich rock layer, and the mechanical properties of the frozen wall need to be studied by comprehensively considering the effects of its internal pore ice content and freezing temperature. In this paper, the mechanical parameters of pore ice and rock are equated by applying the mixing law theory of meso-mechanics, and the Weibull distribution is used to describe the probability of micro-elementary damage, and the damage constitutive model of rock considering pore ice is established. The validation results of triaxial compression tests show that the model parameter equivalization improves the fitting accuracy of the stress-strain curve for the whole process of freezing sandstone significantly, which is about 7.22% higher than that of the conventional model. The results of the evolution analysis of the characteristic parameters m and F confirm the enhancement effect of pore ice on the homogenization and average strength of the rock mass. In addition, the physical significance of the model parameter system is clear, with a view to providing theoretical references for the study of rock mechanical properties and the design and construction of artificial freezing engineering under low-temperature environment.
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循环荷载作用下饱和土石混合料侧限变形试验研究

HE Feng, XU Yong-qing, HU Sheng-liang, LI Hai-chao, TONG Chen-xi

Abstract: (61) HTML (0) PDF (0.00 ByteKB) (0)

Soil and rock mixtures are commonly used as subgrade fill materials for mountain airports. When subjected to cyclic loading, they experience cumulative deformation, leading to uneven settlements that can compromise the stability of the upper foundation. To understand this deformation pattern, a series of dynamic compression tests was conducted on soil and rock mixtures. The study analyzed how the specimen's cumulative deformation changed with the number of cyclic loads across different stone contents and confining pressures, and it developed a corresponding mathematical model. Results showed that, at a fixed stone content, higher confining pressure resulted in greater maximum axial cumulative deformation, with the rate of increase accelerating as stone content increased. The deformation curve typically has two phases: an initial rapid accumulation of axial deformation during cyclic loading, followed by a slower growth as the specimen densifies. Based on these findings, a simple model describing the law of cumulative deformation was proposed, which aligned well with experimental data. The study also examined how excess pore water pressure in saturated specimens evolves during cyclic loading, noting its rapid buildup and slow dissipation, providing valuable insights for managing differential settlement and assessing the stability of mountain airport subgrades.
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Study on the Flexural Performance of Cement-Based Plant Fiber Prefabricated Composite Long Slab

zhangwangxi, huanghe, zhangchen, xieixiangrong, yuanchao, yiweijian

Abstract: (29) HTML (0) PDF (0.00 ByteKB) (0)

To study the flexural performance of 5.1-meter-long cement-based plant fiber fireproof and thermal insulation prefabricated composite slabs, this paper conducted four-point bending tests on four full-length composite slabs, analyzed their failure characteristics, crack characteristics, strain laws, ultimate bearing capacity and ductile coefficient, and discussed the influence of different protective layer thicknesses under positive and negative bending moment loading. The results show that the specimens with positive and negative bending moments present different failure characteristics. The prominent manifestation is that the prefabricated bottom plate of the specimens with positive bending moments shows no obvious phenomenon before failure and presents brittle failure characteristics. At this time, the load will have a certain amplitude of "steep drop", and eventually the crushing phenomenon occurs in the compression zones of both. This composite long plate is lightweight, has good bearing capacity and good ductility. Among them, the positive bending moment specimen has a higher ultimate bearing capacity than the negative bending moment specimen by approximately 50% due to the high tensile strength of the prefabricated bottom plate in the tensile zone and about 23% higher than the cast-in-place slab with the same cross-section. The negative bending moment specimen has a lower bearing capacity than the cast-in-place slab due to the lower compressive strength of the plant fiber cement-based material in the compression zone. The prefabricated base plate placed in the tensile zone can significantly inhibit crack propagation. The crack spacing of the specimens with positive bending moment is 20% to 30% smaller than that of the specimens with negative bending moment. Finally, based on the assumption of the flat section and by using the existing specification formulas, the loading mode coefficient was introduced and a correction formula for the cracking bending moment was proposed. The error between the theoretical calculation value and the test value is less than 5%. The research shows that this correction formula can provide a reliable basis for the calculation of the cracking bending moment of this new type of composite slab.
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Study on Fragility Functions of H-Shaped Steel Columns

ZHENG Shansuo, ZHAO Wang, YANG Song, LI Yongming, LIU Liguo

Abstract: (26) HTML (0) PDF (0.00 ByteKB) (0)

H-shaped steel columns are critical components in steel frame structures, necessitating performance-based seismic assessment. Fragility functions—cumulative distribution functions reflecting the probability of engineering demand parameters (EDP) exceeding damage thresholds—are pivotal but lack codified frameworks compliant with Chinese standards. This study integrates 94 global low-cycle reversed loading test datasets for H-shaped steel columns, adopting drift ratio as the EDP. Three damage states are classified based on structural degradation patterns, with tailored repair strategies. Fragility functions conforming to lognormal distribution are established using the FEMA P-58 methodology. The effects of axial compression ratio and cross-section classification are analyzed. Key findings: Elevated damage states significantly increase fragility function medians; Higher axial compression ratios accelerate plastic hinge formation and strength degradation, reducing medians; Reduced cross-section width-to-thickness ratios delay local buckling, enhancing medians; Cross-section classification outweighs axial compression ratio in influencing fragility curves. The proposed framework aligns with Chinese codes, addressing a research gap and supporting seismic resilience evaluation of steel structures.
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Optimization of Room Air Conditioners for Uniform Thermal Environments

QIU Xiangwei, ZHAI Yingxian, LIU Zhilong, LI Ziqiao, LIU Meng

Abstract: (39) HTML (0) PDF (0.00 ByteKB) (0)

With increasing public demand for indoor environmental quality and the frequent occurrence of extreme high-temperature weather, air conditioning has become an essential means for elderly Chinese individuals to maintain a comfortable thermal environment. However, traditional air supply designs or improper placement of air conditioners can lead to uneven temperature distribution, characterized by "cooler near the unit and warmer farther away." To alleviate discomfort, the elderly often increase fan speed or lower the temperature, resulting in energy waste and health risks. To address this issue, this study proposes a dual-layer near-far circulating air supply method based on ultra-low Mach number counter-rotating fans and annular rotating jet technology. Tests in a controlled climate chamber and home scenario evaluations with 20 elderly participants demonstrated that this technology maintains a longitudinal temperature difference within 0.7°C in a 40 m2 room (0.1–1.7 m range), with a near-end (within 2.0 m) temperature difference below 1.0°C. The elderly felt cooler within 10 minutes and achieved thermal comfort in all areas after 60 minutes, with minimal draft sensation. This technology effectively improves indoor temperature uniformity and thermal comfort, providing technical support for future intelligent air conditioning systems designed for elderly care.
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Study on model tests and mechanical mechanism study of drainage rigid pile in coral sand foundation under horizontal cyclic loading

HUANG Li, WANG Buxin, YANG Xin, ZOU Tan, CHEN Zhixiong

Abstract: (69) HTML (0) PDF (0.00 ByteKB) (0)

To address the critical issue of pile foundations in coral sand foundations subjected to wave-induced cyclic loading during island and reef construction, this study investigates the pile-soil interaction mechanisms of drained rigid piles under static and cyclic horizontal loading through model tests. Firstly, static loading tests determined the ultimate bearing capacity of the drained rigid pile to be 376 N. It was found that the peak bending moment occurred at a depth of 2 to 2.8 times the equivalent pile diameter below the foundation surface, and the slope of the p-y curves flattened with increasing embedment depth. Furthermore, a comparative study on the dynamic response of drained rigid piles and conventional rigid piles under horizontal cyclic loading revealed that: The pile head displacement and extreme bending moment values of conventional rigid piles were greater than those of drained rigid piles. The peak bending moments for both pile types occurred at depths of 3 to 4 times the equivalent pile diameter below the foundation surface. The slopes of the p-y curve hysteresis loops for both conventional and drained rigid piles increased with greater soil depth. However, the drained rigid piles exhibited smaller attenuation amplitudes in both soil resistance and dynamic stiffness compared to conventional rigid piles, while simultaneously demonstrating greater maximum soil resistance and dynamic stiffness. The research demonstrates that drained rigid piles significantly enhance the bearing stability of coral sand foundations under cyclic loading, offering valuable insights for the design of pile foundations in island and reef engineering projects.
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Study on Shear Strength Influencing Factors of Transparent Soft Rock

Zeng Youheng, XIONG Peixi, Fang Xiangwei, QIAO Longjiang, TANG Guangchun, HUANG Sheng

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

Transparent soft rock exhibits significant application value in geotechnical engineering model tests, yet systematic studies on the factors and mechanisms influencing its shear strength remain limited. In this study,fused quartz sand, nano-scale hydrophobic silica powder, No. 15 white oil, and n-dodecane were selected as primary transparent cementing materials to investigate the effects of silica powder content, quartz sand particle size, and sample dry density on the shear strength of transparent soft rock. Theoretical values of cohesion and internal friction angle for the Chongqing Jigongzui Tunnel model test were determined using dimensional analysis. Orthogonal experiments were conducted to optimize the material ratio and further analyze these influencing factors.Results demonstrate that, Increased silica powder content leads to an approximately linear enhancement in cohesion, while the internal friction angle remains nearly unaffected.Higher proportions of fine particles result in an initial decrease followed by an increase in internal friction angle, with negligible impact on cohesion.Elevated dry density induces a rapid-to-gradual ascending trend in cohesion, while the internal friction angle exhibits initial stability followed by a progressive increase.The optimized ratio (4% silica powder, particle size group D with 75% 0.5-1 mm particles, and dry density of 1.35 g/cm3) shows high compatibility with the surrounding rock parameters of the Chongqing Jigongzui Tunnel. This research provides theoretical and technical foundations for applying transparent soft rock in geotechnical model testing..
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Keywords: Temperature Prediction in Box Girders; Genetic Algorithm (GA); CNN-BiLSTM-Attention; Meteorological characteristics; Model evaluation; Hyperparameter Optimization

WANG YU CHEN, ZHANG FANG, YUAN JUNJIE, LIN SHICHEN, CONG LONGYU

Abstract: (90) HTML (0) PDF (0.00 ByteKB) (0)

Concrete box-girder bridges subjected to non-uniform temperature fields are prone to thermal stress-induced cracks and deformation, which seriously threaten structural safety and durability. Accurate prediction of the temperature field serves as the critical foundation for real-time monitoring, damage early warning, and preventive mitigation strategies. To address the insufficient accuracy of discrete-point temperature predictions under multi-factor meteorological features, this study proposes a GA-optimized CNN-BiLSTM-Attention temporal model. The model integrated Bidirectional Long Short-Term Memory (BiLSTM) networks to capture bidirectional temporal dependencies in time-series data, and integrated Convolutional Neural Networks (CNN) to extract localized spatial features from time-series data, while further incorporating a self-attention mechanisms to dynamically assign weights to meteorological parameters, thereby enhancing sensitivity to critical features driving temperature variations. Concurrently, GA is employed to optimizes hyperparameters ( the number of hidden units, learning rate, etc.) to improve prediction stability and generalization capability. Validation results based on field monitoring data from Nanchong Jialing River Bridge demonstrated that the model's superior performance in both short-term (S1 segment) and long-term (S2 segment) predictions, achieving RMSE values as low as 0.178 and 0.129 respectively, with the coefficient of determination (R2) approaching 0.99. Compared to baseline models (e.g.,LSTM, BiLSTM), the error reduction exceeds 20%, while its capability to capture temperature peaks exhibited substantial enhancement. This research validated that the hybrid model integrating spatiotemporal feature fusion and dynamic weight allocation effectively could resolve complex meteorological coupling mechanisms, while providing a high-precision temperature field prediction tool for bridge structural health monitoring. This advancement possessed significant engineering implications for enhancing infrastructure service life and advancing safety-oriented operation and maintenance practices.
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Study on Contaminant Transport Mechanisms in Clay Liners under Varying Saturation Conditions

Hou Shiwei, SHAN Xinyuan, Meng Suyun, Du Xiuli

Abstract: (49) HTML (0) PDF (0.00 ByteKB) (0)

As a critical factor governing pollutant migration rates, soil saturation directly influences the long-term impermeability and contaminant retention efficacy of clay liners in landfills. To elucidate the impact of saturation-dependent mechanisms of pollutant transport in practical clay liners, a dynamic coupled model for contaminant migration in unsaturated soils was developed in this study. Based on mass and energy conservation principles, the generalized Darcy’s law was integrated into the framework, while dynamic variations in soil transport properties and physical characteristics were rigorously accounted. The governing equations for unsaturated soil consolidation, pore water flow, heat transfer, and contaminant transport were systematically formulated to establish the multi-physics model. Numerical simulations of the constructed model were conducted using the finite element analysis platform COMSOL Multiphysics, with case studies implemented to validate the model's rationality in civil engineering scenarios. Further analysis was conducted on the temporal evolution patterns of pore fluid pressure, contaminant concentration, and soil settlement under variations in saturation. Results demonstrate that pore fluid pressure transitions from shallow negative pressure to global negative pressure during consolidation, with 1–4 kPa higher pressure values being observed under high-saturation conditions (Sr > 0.85) compared to medium-low saturation cases; Solute migration rates were found to increase by 10%–25% with elevated saturation, exhibiting nonlinear attenuation with depth; Soil settlement, characterized by a nonlinear trend, peaked at approximately one year, where 5%–10% greater maximum settlement was recorded in high-saturation scenarios (Sr > 0.85) than in low-saturation cases.
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A modified method predicting the trajectory and holding capacity of drag anchors in sand

LI Da, LI Shuzhao, SUN Guodong, SONG Yonghao, WANG Dong

Abstract: (69) HTML (0) PDF (0.00 ByteKB) (0)

Drag anchors have the high anchor efficiency and low manufacturing cost, and are widely used for the mooring of offshore floating platforms. However, there are often non-negligible errors in the prediction of the anchor penetration and holding capacity when the drag anchor is installed in sand. A modified method was developed to predict the installation process of the drag anchor, which divides the whole installation process into several incremental steps and allows the bottom surface of the fluke to separate from sand. At each incremental step, the limit equilibrium equations of the anchor and soil in failure are established to obtain the holding capacity, and the increment of the horizontal displacement, burial depth and rotation were calculated, based on the principle of minimum force to drag the anchor, with a reasonable direction specified for the drag anchor motion. Small-scale model tests were conducted on drag anchors with two types of the shank length, and the relative density of the sand sample was 47%. The holding capacity and position of the anchor were measured in real time. During the tests, it was observed that the bottom surface of the fluke already separated from the sand sample in the early stage of installation, and the burial depth of the anchor still increased with the increment of the holding capacity, which proved the rationality of the assumption of separation in the modified method. The rationality of the modified method was verified by comparing the measured values and predicted values of the anchor trajectory and holding capacity. Both the test results and calculation results indicate that, when the shank length increases from 30 cm to 36 cm, although the penetration depth of the anchor padeye and the rotation of the anchor body decrease, the final holding capacity still increases by 18%.
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Experimental investigation on axial compression behavior for prefabricated reinforced UHPC tube infilled with seasand seawater concrete

jiachenhao, liying, wanglihui, wangyaohong

Abstract: (53) HTML (0) PDF (0.00 ByteKB) (0)

The utilization of sea sand to produce seawater sea sand concrete (SSC) can address the shortage of river sand resources in construction projects.Seasand Seawater Concrete (SSC) demonstrates significant advantages in addressing the shortage of river sand resources in engineering construction. However, it faces critical challenges such as high chloride ion content and corrosion-susceptible steel reinforcement. Ultra-High Performance Concrete (UHPC), known for its exceptional high strength, impermeability, and durability, faces limitations in widespread application due to prohibitively high material costs. This study proposes a novel ?precast steel-reinforced UHPC tube encased SSC composite column (RUHPC-SSC composite column) by leveraging the physical-mechanical properties and complementary advantages of SSC and UHPC. Spirally confined UHPC tubular shell acts as a permanent structural formwork for casting the SSC core, providing both confinement and corrosion resistance. Axial compression static tests were performed on 12 composite short columns, and the influence of volumetric spiral reinforcement ratio and diameter-to-thickness ratio parameters on the axial compressive performance was systematically investigated. The experimental results suggest that the failure mode of the RUHPC-SSC composite column is oblique shear compression failure, with the UHPC tube maintaining structural integrity post-failure. The peak bearing capacity of the RUHPC-SSC composite column exhibits a negative correlation with the spacing of spiral stirrups in the UHPC tube and a positive correlation with the diameter-to-thickness ratio. Compared to monolithic RSSC columns, the RUHPC-SSC composite column achieves a 139.8% increase in peak bearing capacity. The UHPC tube-spiral stirrup synergy boosts both strength and deformability of the composite column.
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Study on the correlation between physical environment parameters and passenger satisfaction in the waiting room of high-speed railway station in summer

DONG WENJING

Abstract: (75) HTML (0) PDF (0.00 ByteKB) (0)

The waiting hall's environmental quality directly impacts passengers' travel experience. The high temperatures in summer impose higher requirements on the physical environmental parameters of high-speed rail station waiting halls. By investigating and monitoring the indoor physical environment of waiting halls in different regions of China during summer, this study analyzes passenger satisfaction survey data from corresponding stations to explore the relationship between the physical environment quality of these waiting halls and passenger satisfaction. Through systematic field measurements, key physical environment parameters such as temperature, humidity, noise, illumination, PM10 levels, and carbon dioxide concentration were collected in detail from 11 high-speed railway stations. The indoor physical environment status of different station waiting rooms during summer was compared and analyzed while collecting passenger satisfaction feedback through questionnaire surveys. Based on environmental monitoring data and questionnaire results, an analysis is conducted to determine the quantitative relationship between overall satisfaction with the physical environment (including thermal environment, light environment, sound environment, and air quality) in high-speed railway station waiting halls during summer using factor analysis and multiple linear regression methods. The results indicate that during the summer season, passenger satisfaction is primarily influenced by temperature, followed by air quality and sound environment. The impact of light environment on overall satisfaction is found to be relatively minimal. In terms of the thermal environment, there is a strong correlation between humidity and ventilation with overall satisfaction regarding the physical environment. This is followed by the uniformity of temperature distribution and actual temperature. In the acoustic environment, noise factor and broadcast clarity exhibit a significant correlation. The illuminance in the light environment is more important, while air pollutants and air quality freshness account for a relatively substantial proportion.
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Analysis of Compressive Permeability Characteristics of dredged mud under Sorting Effect

lv tongwei, zhang yong, weng Jiaxing, zeng lingling

Abstract: (56) HTML (0) PDF (0.00 ByteKB) (0)

Sorting effect is common in the process of blowing and deposition of dredged mud, which inevitably leads to differences in the distribution of mechanical properties of dredged mud. For the sandy dredged mud, the indoor sedimentation column modeling test was used for sedimentary sorting to form the sorted soil samples in different states, and the compression and permeability properties of the soil body were investigated through the one-dimensional consolidation-permeability test. The results show that the compression and permeability of the soil samples change significantly after sorting, and the compression of the bottom soil sample is obviously smaller than that of the top soil sample; and the permeability coefficient of the bottom soil sample is obviously larger than that of the top soil sample. It was also found that the difference in permeability coefficients after sorting action was related to the pore ratio as well as the fines content, and for soil samples with fines content FC>30 %, a clear quantitative relationship was presented between the pore ratio and the pore ratio at the liquid limit; while for soil samples with fines content FC≤30 % a prediction formula for the permeability coefficient was given.
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Model test and modified continuous hidden Markov model-based safety evaluation of high arch dam

Shen Chen, Shaowei Hu, Jinghao Li, Liwen Zheng

Abstract: (93) HTML (0) PDF (0.00 ByteKB) (0)

The safety assessment is of great significance for ensuring long-term safe operation of high arch dams. The machine learning algorithm of Continuous Hidden Markov Model (CHMM) has strong capabilities in processing multi-sourced time sequential continuous data, establishing relationship between complex data, and real-time accurate evaluation. Therefore, it has great applicable potential in high arch dam safety evaluation. However, the whole-process safety evaluation of overloading failure of high arch dams via CHMM-based multivariate indices analysis has not been carried out yet. Therefore, this paper carried out an overloading test on a physical model of a high arch dam, monitored the time series of cracks and deformations throughout the dam's failure process, and constructed a high-quality CHMM dataset with low noise and stability. Subsequently, CHMM was applied to the safety assessment of high arch dams, and a new rule for state transfer matrix ordering was proposed to give meaning to the state labels, which improved the readability of the results of CHMM. Finally, the whole-process safety variation of arch dam model was evaluated by the CHMM optimized state sequence, and validated with observed results. The results indicated that CHMM-based state sequence classified the safety status of tested high arch dam into seven levels, which coincide with the time-sequential evolution of deformation and crack, and further proposed the featuring overloading safety. The failure process of tested high arch dam was categorized into quasi-linear, nonlinear of large deformation, arching effect action and complete failure stages with respective overloading safety degrees of 2, 6, 10 and 14. This study provides the new insight into safety evaluation of high arch dam and makes reference for early-warning of high arch dam.
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A dynamic control method for shield tunneling parameter thresholds based on decoupling analysis of boreability

wang jian jun, li tong, rong xue ning, wang jia jun, liu peng

Abstract: (64) HTML (0) PDF (0.00 ByteKB) (0)

In order to reduce the health risk of equipment due to excessive cutterhead torque fluctuation, the overload and fluctuation of cutterhead torque need to be dynamically suppressed. The dynamic control thresholds of tunneling parameters under the constraint of tunneling efficiency control law is explicitly derived to reveal the suppression strategy on the basis of decoupling the network influence mechanism among geological parameters, tunneling parameters and rock mass boreability through the combinational two-factor analysis. The results show that: the combinational two-factor analysis can learn the low-dimensional characteristics of the mechanism of differential interaction within the rock mass boreability control factors, the multigroup monotonicity analysis and the elliptic conic envelope model can explain the influence mechanism of the factors on boreability. The elliptic conic envelope model can accurately determine the overload risk of cutterhead torque in the form of analytical model in multiple stratum. In the risk management and control task against the tunneling parameters fluctuation and the key components damage of shield, the dynamic control method for shield tunneling parameter thresholds based on decoupling analysis of boreability can provide explicit decision instructions and the control chain of fast command response. The output of the instruction layer of the control method is interpretable for the two-dimensional projection of the elliptic conic envelope equation can be transformed into a dynamic threshold model of tunneling speed with the cutterhead torque thresholds as the control goal under the constraint of tunneling efficiency control law. The command logic of the application layer is prior-determined single factor control, which can not only respond to dynamic instructions quickly, but also enhance the steady state of tunneling parameters.
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Freeze-thaw durability of sulfate saline soil stabilized with SH agent

weili, liuqingya, changxinxin, chaishouxi

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Winter freezing and spring thawing cause engineering geological issues such as frost heave cracking, thaw settlement, and boiling subsidence in sulfate saline soil embankment construction. To this end, freeze-thaw test, unconfined compressive strength test, SEM test and CT test were completed on sulfuric saline soil stabilized with lime, SH agent, and fiber to study the mechanical properties degradation and the microstructure damage characteristics under freeze-thaw conditions, clarifying the influence mechanism of the SH agent and fiber on the freeze-thaw durability of the soil. The results show that the UCS of soil exhibited a stage-wise change, with a large decrease, small decrease and stable strength as the number of freeze-thaw cycles increased. With the increase of freeze-thaw cycles, the area ratio and the equivalent diameter of soil particles decreased, some aggregates were broken, and the morphology of soil particles gradually transitioned from elongated to circular. Fiber reinforcement reduces the porosity of soil, and the number of small pores gradually reduced, and the number of medium pores and large pores increased little by little. The number of cracks increases, and they gradually extend from the surface of the specimen into the interior. Sulfate saline soil stabilized with 12% lime, 3% SH agent and 0.3% fiber is a more suitable mix ratio. SH agent wraps soil particles and fills soil pores, as well as the interface interaction between fibers and soil and the spatial network structure formed by fibers, which improves the mechanical properties and freeze-thaw resistance of sulfate saline soil.
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Experimental study on the ground disturbance characteristics during shield tunneling in high cobble content strata

SONG Weitao, ZHANG Pei, DU Xiuli, LIN Qingtao

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Compared with ground with low cobble content, a high cobble content strata has characteristics such as large particle pores and point-to-point contact between particles, etc. During shield tunnelling, the large-grained skeleton structure in such strata is more prone to damage, leading to an unstable state. Based on a typical shield tunnel project, a model shield machine that can achieve functions such as cutterhead rotation and spiral discharging soil is used to conduct model test. Shield model tests all were achieved for both shallow tunnel (1.0 D) and deep tunnel (2.0 D) in high cobble content strata (rock content of 70%). Then, from the aspects of shield tunneling mechanical parameters, ground surface settlement curves and excavation face stability, the ground disturbance characteristics of shield tunnelling in high cobble content strata are analyzed. Test results show that for the high cobble content strata, under the same shield advancement parameters, the screw excavator torque shows little difference between shallow and deep tunnels. However, the stable value of cutterhead torque in shallow tunnel is less than that in deep tunnel. Under these two ground conditions, the ground surface settlement curves all show an asymmetric distribution about the tunnel centerline, and the eccentric position is related to the rotation direction of the cutterhead. When the cutterhead rotates clockwise, the symmetry axis of the settlement curve is located on the left side of the advancing direction. The failure modes of excavation face in both shallow and deep tunnels all present to be global instability, with collapse zones encompassing soil both ahead of and behind the cutterhead. Besides, the ground collapse morphologies induced by discharging soil or cutterhead retraction are all elliptical, with the major axis perpendicular to the shield advancement direction. However, the extent of ground collapse caused by discharging soil is larger than that induced by retraction failure, which is closely related to the corresponding ground loss.
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Experimental study on punching shear capacity of slab-column joints with partial use of ultra-high performance concrete

LI Chuang, ZHOU Yan

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This study conducted through the tests of 9 interior slab-column joint specimens with partial utilization of ultra-high performance concrete (UHPC) under concentrated vertical loads to explore a new method for enhancing the punching shear resistance of such joints. This test examined the impact of UHPC on the performance and damage mechanisms of slab-column joints. The test parameters included the dimensions of the UHPC area as well as the volume fraction of steel fiber present in the UHPC. The test results indicated that UHPC had the potential to substantially enhance the ductility and punching shear capacity of slab-column joints. When UHPC was used locally in an area of one times the slab thickness from the column face, the ductility and punching shear capacity for specimens with a fiber ratio of 0.8% increased by 126% and 64%, respectively, compared to the specimens made entirely of normal concrete (NC). Therefore, the overall performance of the UHPC and NC composite slab-column joints can be enhanced with the rational UHPC area and volume fraction of steel fibers in practice. In this paper, the punching shear resistance of each specimen was estimated by three different codes. It was found that all the code equations either overestimated or underestimated the punching shear capacity within the UHPC region. Therefore, further research is necessary to explore the punching shear capacity of UHPC slabs. The finite element software ABAQUS was used to establish the force analysis model of specimens. The simulation results agree well with the experimental results. Based on this model, the effect of different UHPC area on the punching shear capacity of the specimens was further investigated. Finally, an empirical formula for estimating the punching shear capacity of UHPC–NC composite slab-column joints is proposed. The predicted values obtained from this formula show good agreement with the numerical results.
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Analysis of Lateral Bearing Behavior and Reliability for Flexible Monopiles in Spatially Variable Sandy Soils

tongquangang, wangchendi, chenyingjie, zhangyunfei, yijiangtao

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Geotechnical materials exhibit significant heterogeneity in their spatial distribution due to the combined effects of sedimentation processes, geological history, and environmental factors. Traditional design methods for horizontally loaded piles assume that soil parameters are spatially homogeneous constants and use idealized calculation models for analysis, which often leads to an overestimation or underestimation of the horizontal bearing capacity of pile foundations. This study employs the stochastic finite element method and selects the internal friction angle of sandy soil as a key variable parameter. It systematically investigates the influence mechanisms of the spatial variability coefficient of sandy soil, horizontal and vertical correlation distances on the horizontal bearing characteristics and failure probability of flexible single piles. The results show that the spatial variability of the internal friction angle of sandy soil significantly affects the horizontal bearing performance of the pile foundation: as the variability coefficient of the internal friction angle and the vertical correlation length increase, the mean horizontal ultimate bearing capacity decreases, while the coefficient of variation of the bearing capacity increases. This indicates that the spatial variability of the soil not only reduces the average bearing capacity but also increases the dispersion of the bearing capacity. Further analysis of seven typical variability combinations reveals that the failure probability of flexible single piles generally exceeds 50%. Based on these findings, this study innovatively establishes an explicit functional relationship between the safety factor and failure probability, providing a theoretical foundation and practical tool for the reliability design of horizontally loaded piles.
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Experimental study on performance connection of threaded sleeve of steel tie rod

Huang Hao, Zhou Ting, Yang Wei, Wang Xinyan

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As the core load-transferring component in long-span suspended structures, the reliability of sleeve connection joints in steel tie rods directly affects the overall structural safety. To investigate the influence of thread engagement depth and sleeve wall thickness ratio on joint bearing performance, this study conducted tensile tests on 12 full-scale specimens with different parameter combinations (6 groups for each parameter), analyzing typical failure modes and their evolution patterns under various configurations. A refined numerical analysis system considering threaded contact was established using ABAQUS finite element models. The results demonstrate significant parametric sensitivity in both load-bearing capacity and ductility characteristics. When thread engagement depth is less than 1.0d, uneven interfacial shear stress distribution leads to thread pull-out failure. However, when depth reaches 1.0d or more, the failure mode transitions to ductile necking fracture dominated by rod deformation, with maximum bearing capacity stabilizing. For sleeve wall thickness ratios below 0.225, brittle fracture occurs in sleeves due to stress concentration. When the ratio reaches 0.225 or higher, optimized stress distribution through enhanced sleeve stiffness shifts the failure mode to rod plastic deformation. Comparative analysis between theoretical models and experimental data validated critical condition equations for three failure modes, showing good consistency with error is within 4%. The study ultimately proposes a dual-control parameter design criterion: thread engagement depth should be ≥1.1d combined with sleeve wall thickness ratio ≥0.225, ensuring both high load-bearing capacity and controllable ductility for connection systems. This provides theoretical guidance for engineering applications.
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Optimized dynamic stability analysis of three-dimensional dam slope considering strain-softening of rockfill

PANG Rui, YAO Hao-yu, XU Ming-yang, ZHOU Yang, XU Bin

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The stability analysis of high earth-rockfill dam is mostly limited to two-dimensional situation, and there is no suitable three-dimensional stability analysis method. In addition, the rockfill material of earth-rockfill dam is prone to strain softening under strong earthquakes, which affects the seismic performance of the dam. It is necessary to develop a three-dimensional stability analysis method for high dams that can take the softening effect into account. Firstly, a three-dimensional static and dynamic stability analysis method for high earth-rock dams is proposed based on the finite element sliding surface stress method combined with the optimized horn-shaped three-dimensional damage mechanism. Then, the relationship between post-peak strength and post-peak shear strain is obtained by processing the triaxial test results of rockfill in order to consider the impact of the softening effect of the rockfill material. Finally, the developed stability analysis framework is applied to analysis the static and dynamic stability of three-dimensional high earth-rockfill dam, and is compared with the two-dimensional case. The results show that the slippage with and without considering the softening effect differ significantly, and this difference increases as the cumulative slippage increases. Compared with the three-dimensional stability analysis, the two-dimensional stability analysis based on cumulative slippage tends to underestimate the seismic stability of the dam slope.
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Residential Air Conditioning Energy Fractal Analysis and Short-Term Prediction Model Optimization

FU CHENGHAO, Liu Meng, Li Ziqiao

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The energy consumption of air conditioning systems in residential buildings is significantly influenced by the diversity of user behaviors. Traditional statistical features struggle to accurately discern differences in usage patterns under conditions of inadequate data quality, rendering short-term energy consumption prediction models challenged in balancing accuracy and computational cost. Fractal theory, however, offers a distinct advantage in addressing these challenges by quantifying the nonlinear and multi-scale complexity of time series data, thereby enabling the differentiation of user behavior patterns. This study proposes a short-term energy consumption prediction framework that integrates fractal analysis with a data-driven approach. By employing fractal features, users are categorized into low, medium, and high complexity groups, with input data and features optimized across sliding window size, data volume, and feature selection to mitigate noise interference, preserve key patterns, and balance prediction accuracy with computational efficiency.. Based on summer residential air conditioning data, the study finds that sliding window size is negatively correlated with complexity: low-complexity groups prefer longer windows, while medium- and high-complexity groups require shorter ones. For data volume, low- and medium-complexity groups need less, whereas high-complexity groups demand more comprehensive data. In feature selection, low- and medium-complexity groups rely on large-fluctuation features, while high-complexity groups depend on small-fluctuation features. Validation with a 2000-household sample demonstrates a MAPE of 9.82% and a CV-RMSE of 11.40%, achieving a 41.52% error reduction compared to per-household prediction models while significantly saving computational time. By combining fractal features with K-means clustering and LSTM networks, this study overcomes limitations of conventional approaches, offering an efficient solution for short-term energy consumption prediction in residential settings.
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Investigation of Hydro-Thermal-Salinity Distribution in Subgrade Saline Soils of Cold and Arid Regions

YUAN Chao, ZHANG Tong wei, LIU Zi jian, YAN Lu chun, HONG Wei, LIU Qi, WU Zi long

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Saline soils, which are widely distributed in the cold and arid regions of northwest China, are prone to salt swelling and solution-induced subsidence under changing hydrothermal conditions. Due to variations in evaporation boundaries, the distributions of hydro-thermal-salt fields and the stratified deformation behaviors of different subgrade structures remain poorly understood. This study, based on the Liuyuan–Dunhuang Expressway project, investigated three types of pavement structures: concrete shoulder with a semi-rigid base, gravel shoulder with a semi-rigid base, and gravel shoulder with a flexible base. Multi-physical field monitoring was carried out, including measurements of volumetric water content, temperature, and electrical conductivity. For each pavement structure, 30 temperature sensors and 9 soil water-salt composite sensors were installed. To better interpret the physical significance of the monitoring data, coupled hydro-thermal-mechanical-salt numerical simulations were subsequently conducted. The monitoring results indicate that the gravel shoulder combined with a flexible base provides advantages in thermal insulation and in inhibiting water and salt migration. Under identical conditions, this structure improves road drainage, enhances evaporation capacity, and strengthens thermal insulation performance. Therefore, in saline soil environments, this structural configuration effectively mitigates the accumulation of water and salt in the subgrade, thereby extending its service life.
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Study on the Compressive Bearing Performance of Masonry Walls Reinforced with Double-Sided Prefabricated Autoclaved Aerated Concrete Panels

ZHOU Yongming, PAN Shuhan, SHI Tao, GAO Chao, LI Guohua, XU Weibin, CHEN Ruisheng

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To investigate the compressive bearing performance of brick masonry walls reinforced with prefabricated autoclaved aerated concrete (AAC) panels, two brick masonry walls reinforced with double-sided prefabricated AAC panels and two unreinforced brick masonry walls as control specimens were designed and fabricated. Through compressive bearing capacity tests and finite element simulation software, the failure modes and compressive bearing performance of the brick masonry walls reinforced with prefabricated AAC panels were studied. Both the experimental and simulation results indicate that the reinforced layer of prefabricated AAC panels can provide confinement to the wall, delaying the cracking of the brick masonry wall and enhancing its compressive bearing capacity, ductility, and integrity. Compared to the unreinforced masonry walls, the compressive bearing capacity of the double-sided prefabricated AAC panel-reinforced walls increased by a maximum of 71.3% in the tests and by a maximum of 67.5% in the simulations. Based on the failure modes of the specimens and considering the contribution of the prefabricated autoclaved aerated concrete panel reinforcement layer, a formula for calculating the compressive bearing capacity of this reinforcement method was proposed. Furthermore, the strength utilization coefficient of autoclaved aerated concrete for this calculation method was fitted and determined based on the experimental and simulation results.
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The influence and kinetic analysis of limestone powder dosage and fineness on cement hydration process

ZHAO Boxun, SUN Huamin, TAN Yong, MIAO Chaojie, WU Hao, YU Linwen

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In this study, a microcalorimeter was used to analyze the hydration heat of cement pastes with different contents and fineness of limestone powder. Based on the Krstulovi?-Dabi? model, the actual hydration reaction rate curve and the theoretical hydration reaction rate curve of each stage were obtained. The reaction kinetics related parameters including degree of reaction, reaction order, and reaction rate constants for the NG, I, and D stages were calculated to analyze the influence of limestone powder content and fineness on cement hydration. Experimental results demonstrate that within the limestone powder dosage range of 0~35% and specific surface area of 465 m2/kg ~665 m2/kg, the correlated increase in both parameters enhances cement hydration kinetics, resulting in both elevated hydration heat peaks and accelerated peak occurrence. When the limestone powder content is 35%, the peak increases by 26.2% and occurs 3.17 hours earlier. Additionally, the reaction degree of the NG process (crystallization nucleation and crystal growth process) of cement hydration increases. The addition of limestone powder and the increased fineness enhance the early hydration reaction rate, while leading to a limited hydration degree in the later-stage.
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Study on the dissolution characteristics and meso-structure damage evolution of Qixia Formation limestone under dissolution

Zhang Limin, Wang Hai, Li Wenqiang, Li Renjie, Ji Feng

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Carbonate rocks, widely distributed, undergo significant alterations in their macro-scale and meso-scale characteristics and mechanical properties due to dissolution processes, which may trigger geological disasters. This study investigates Permian Qixia Formation limestone, selected as the research subject, using cylindrical thin sections prepared for experimentation. Carbonate karst dissolution experiments were conducted at varying temperatures (0°C, 15°C, 25°C, and 40°C) and solution pH values (pH = 1, 3, 5, 7) to assess the mass loss of carbonate rocks and changes in solution pH due to dissolution. Scanning electron microscopy (SEM) was utilized to examine changes in fracture and porosity of the carbonate rock and to explore the mechanism of meso-structural damage evolution. The results indicate that both rock mass loss and solution pH increase with dissolution time, while the dissolution rate decreases over time. At pH = 1, the cumulative mass loss of the sample reaches 11%, with a maximum mass loss rate of 1.3%/h. Both the mass loss rate and total loss are several orders of magnitude greater compared to conditions where pH > 3. Furthermore, the rate of pH increase at pH = 1 is significantly slower than under other pH conditions. A solution pH of 6 serves as the threshold for distinguishing mass loss characteristics during dissolution: when pH < 6, chemical dissolution predominates, whereas physical erosion dominates when pH > 6. Under identical pH conditions, higher test temperatures result in greater cumulative rock mass loss and higher post-experiment solution pH. Additionally, carbonate karst erosion exhibits beaded dissolution pores along macro-scale fractures, cystic porosity at fracture tips, and enhanced dissolution along grain boundaries at the meso-scale. The findings provide an important scientific foundation for further exploring the dissolution process of carbonate rocks.
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Mechanical properties of different fiber reinforced ultra-high performance concrete after high temperature

Wu Pengtao, Zhang Xueyan, Liu Zhongxian

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The apparent characteristics and mechanical properties of ultra-high performance concrete reinforced by different fibers were studied by using high temperature heating and high temperature compression strength tests on the cylinders. Aiming at different temperatures, fiber content and fiber types, 108 specimens of ultra-high performance concrete cylinders were prepared, and uniaxial compression tests were carried out at 6 target temperatures (20℃, 200℃, 400℃, 600℃, 800℃, 1000℃). The effects of single steel fiber, mixed steel fiber of different lengths, mixed steel fiber and polypropylene fiber, mixed steel fiber and polyethylene fiber on high temperature cracking and compressive strength of ultra-high performance concrete were compared. The results show: with the increase of temperature, the damage degree of ultra-high performance concrete becomes more serious. After high temperature action, the mixed steel fiber and polypropylene fiber ultra-high performance concrete can also maintain good integrity and high compressive strength, and can still maintain 30% residual strength after high temperature action at 1000℃. With the increase of temperature, the compressive strength of ultra-high performance concrete increases and then decreases, and the ductility of ultra-high performance concrete is enhanced by high temperature.
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Regional energy and economic affordability study of air source heat pump electric heating in rural areas of northern China

Xiaoyi Chen, Ziqiao Li, Wenmao Zeng, Longkang Dai, Xiangwei Qiu, Meng Liu

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Clean heating can mitigate pollution issues in northern China, and affordable cost and security of power supply are keys to promoting clean heating. Therefore, this paper proposed a suitability-evaluation framework for ASHP (air source heat pump) heating in rural areas of northern China from a regional perspective. By establishing regional energy indicators and economic indicators, assess the energy and economic affordability of ASHP heating in rural areas based on scenario analysis. The results showed that regional energy affordability gradually decreased with the increase in residents" heating demand, which is influenced by the regional energy infrastructure, household size, and living habits. Furthermore, in scenarios ranging from basic to high demand, the proportion of heating operation costs in per capita disposable income (PCDI) is less than 10%, showing a high level of economic affordability. However, under medium to high-demand scenarios, the initial investment accounts for a proportion of 10.4% to 24.9% of the PCDI, indicating weak economic affordability. Rural residents require financial subsidies, otherwise, residents may face energy poverty and their acceptance of ASHP heating systems may also decrease. This research provides valuable insights for rural clean heating energy planning and policy-making.
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Pore Tortuosity Calculation Model of Soil-Rock Mixture Considering Particle Breakage

Zeng Ling, Qi Yan, Zhang Hong Ri, Wen Wei, Tang Jing, Xiong Jian Ping, Song Jian Ping, Chen Jing Cheng, Wang Wen Guang, Li You Jun, Long Tong Bo, Xu Zi Hang, Li Lin Le

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Pore tortuosity represents the complexity of fluid flow paths in soil and is a key parameter for analyzing soil infiltration properties. However, most existing pore tortuosity models are general-purpose, making them less suitable for soil-rock mixtures, which exhibit distinct characteristics such as a wide grain size distribution and complex pore structure. To develop a computational model for soil-rock mixtures that accounts for the effects of coarse particle crushing on pore tortuosity, soil particles were assumed to be circular with varying sizes. And a lognormal distribution function was used to represent soil gradation in different cases, while obstruction angle and anisotropy parameter were introduced to characterize the particle dispersion pattern. A pore tortuosity calculation model influenced by multiple factors was finally developed based on the laminar flow of fluids in soil-rock mixtures. Using programming software and numerical simulation methods, seepage simulations were performed on soil-rock mixtures with varying soil gradation and initial porosity. The relative error between the theoretical and simulation results was within 2%, demonstrating the validity of the proposed model. The analysis of the model influencing factors indicated that changes in particle gradation significantly affect pore tortuosity. Pore tortuosity decreased as coarse particle content increased, and the absence of macroparticles further reduced pore tortuosity. As the obstruction angle and anisotropy parameters increased, the pore tortuosity also increased. A significant negative interaction was observed between porosity and the other factors. When porosity is high, pore tortuosity converges to 1, indicating that porosity becomes the dominant factor affecting pore tortuosity. Among the above four influencing factors, the degree of influence on pore tortuosity in the soil-rock mixture followed the order: particle gradation (mass fractal dimension) > anisotropy parameter > porosity > obstruction angle. The grey correlation values of the mass fractal dimension and anisotropy parameter exceeded 0.95, indicating a strong correlation.
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Inversion of Chl a spatiotemporal distribution and analysis of driving factors based on Landsat-8 data

zhangziwei, guoxianhua, wangyazhu, liuqianchen

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Chlorophyll-a (Chla), primarily sourced from phytoplankton, serves as a pivotal indicator for water eutrophication. It stands as a fundamental metric for gauging eutrophication levels, biophysical conditions, and primary productivity within lake ecosystems. Focusing on Taihu Lake as the study area, this research utilizes Landsat 8 OLI data alongside measured point data to establish a partial least squares model for inversion via a semi-empirical approach. Preliminary experimental findings indicate that the derived model and parameters effectively capture Chla concentrations in Taihu Lake over the past nine years (2015-2024). Building upon this foundation, the study integrates physical geography and socio-economic factors to analyze trends in Chla concentrations and their underlying causes. Consequently, this paper furnishes a semi-empirical model, parameter scheme, and a comprehensive long-term dataset of Chla concentration dynamics in Taihu Lake, offering robust support for future governance endeavors concerning the lake"s ecological restoration.
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Investigation on catalytic ozonation of coal chemical RO concentrated water by Mn-Co@4A

WANG Ziran, SUN Wenquan, ZHOU Jun, WU Deyong, QIANG Jinfeng, SUN Yongjun

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In this study, Mn-Co@4A catalyst was investigated for catalytic ozonation of coal chemical RO concentrated water. The Mn-Co@4A catalyst was characterized by SEM, EDS, XRF and XRD. The effects of working conditions (initial pH, catalyst filling ratio, ozone dosage, reactor height-diameter ratio) on the catalytic efficiency of ozone catalytic oxidation wastewater were studied. The stability of Mn-Co@4A catalyst was evaluated under optimal conditions, and the mechanism of water treatment was analyzed by UV absorption spectroscopy, three-dimensional fluorescence spectroscopy and free radical quenching experiments. The results show that Mn-Co@4A catalyst has good catalytic performance and stability. Under the conditions of initial pH = 7.64 (raw water), catalyst filling rate of 5%, ozone dosage of 6 mg/L/min, and reaction column height-diameter ratio of 6 : 1, the best COD removal rate of coal chemical RO concentrated water can reach 69.92%. With the increase of oxidation time, the conjugated structural substances, unsaturated ketones and protein-like substances in the RO concentrated water of coal chemical industry were gradually effectively degraded, and .OH and O2.-played the main role in the oxidation of organic matter.
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Adsorption performance and mechanism of manganese ferrite modified biochar for phosphate

Zhao rui

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Excessive phosphorus discharge is one of the primary factors contributing to water eutrophication, making the development of efficient and cost-effective technologies for phosphorus-containing wastewater treatment crucial for water environment protection. In this study, bamboo biochar (BC) was prepared through pyrolysis using moso bamboo as the raw material, and manganese ferrite-modified biochar (MnFe2O4/Biochar, MB) was synthesized via a hydrothermal method for the removal of phosphate (H2PO42-) from wastewater. The effects of factors such as pH, adsorption time, and initial concentration on the adsorption performance were investigated. The results indicated that the adsorption capacity of MB for phosphate decreased with increasing pH, reaching a maximum capacity of 4.59 mg/g at pH=4.0. The adsorption process followed the Freundlich isotherm model and the pseudo-second-order kinetic model. The high saturation magnetization value of MB (48.28 emu/g) demonstrated its ease of separation. Characterization results revealed that the adsorption mechanism primarily involved the exchange of hydroxyl groups in Mn-OH with phosphate to form inner-sphere complexes. Furthermore, in actual water bodies, the presence of coexisting ions and organic matter interacted with phosphate, providing additional adsorption sites for MB and resulting in favorable phosphate removal performance. The findings of this study suggest that MB, as an efficient and easily separable adsorbent, holds significant potential for application in the treatment of phosphorus-containing wastewater.
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Effect of corrosion behavior on mechanical properties of steel under failure mode of local anti-corrosion coating

niukai, zhangliang, xuweihao, zhouyan, yangyang, wangjunyan, wangpengkai

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This paper focuses on Q355B steel under the condition of local anti-corrosion coating failure to explore the rusting behavior of the steel and its impact on mechanical properties. Standard specimens in three typical local anti-corrosion coating failure modes, namely pitting corrosion, banded corrosion, and surface corrosion, were designed. Based on electrochemical tests, the rusting rate of the steel under the local anti-corrosion coating failure modes was measured, and the rusting morphology and distribution characteristics of the steel were analyzed. The starting points, propagation paths, and morphological changes of local rusting were analyzed based on the test results, and the corrosion paths and mechanisms under the local anti-corrosion coating failure modes were revealed through the corrosion surface morphology. The elastic modulus, yield point, yield strength, tensile strength, ultimate strain, and elongation after fracture of the steel under the local anti-corrosion coating failure modes were analyzed through the steel tensile tests. The results indicate that, the reduction coefficients of the elastic modulus, yield strength, and tensile strength of the steel under the local anti-corrosion coating failure modes have a linear negative correlation with the average corrosion rate; the reduction coefficients of the ultimate strain and elongation after fracture have a nonlinear correlation with the average corrosion rate. This study reveals the influence of local anti-corrosion coating failure modes on the mechanical properties of the steel, and the research results can provide references for the anti-corrosion protection of steel and the structural safety assessment.
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Early Autogenous Shrinkage Performance of PVA-FRCC Mixed with Aeolian Sand

Wang Yuqing, Qu Xun, Yun Zeya, Sang Dade, Liu Shuguang

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In order to study the early autogenous shrinkage performance of polyvinyl alcohol fiber cement-based composites ( PVA-FRCC ) mixed with aeolian sand and establish a autogenous shrinkage prediction model. This paper takes aeolian sand replacement rate, fiber volume rate, water-binder ratio and sand-binder ratio as research variables. The autogenous shrinkage of the material within 7 days was tested by shrinkage test, and the influence of various factors on autogenous shrinkage was summarized. The pore fluid saturation, porosity and pore size of the specimen were tested by low-field nuclear magnetic resonance test. The influence mechanism of aeolian sand on autogenous shrinkage is revealed. The results show that aeolian sand has porous water absorption and small elastic modulus. When the water-binder ratio is small, the autogenous shrinkage increases with the increase of the replacement rate of aeolian sand. When the water-binder ratio is large, the autogenous shrinkage decreases with the increase of the replacement rate of aeolian sand. The internal curing effect of PVA fiber reduces the autogenous shrinkage. When the water-binder ratio is small, the chemical shrinkage caused by the hydration reaction increases, resulting in an increase in autogenous shrinkage ; the increase of sand-binder ratio increases the absolute content of aeolian sand, which leads to the increase of autogenous shrinkage. The overall pore size of PVA-FRCC mixed with aeolian sand is small, and the most probable pore size is about 10 nm. The increase of pore porosity after the increase of aeolian sand replacement rate is the main reason for the increase of autogenous shrinkage. Finally, considering the influence of various factors, the early autogenous shrinkage prediction model of PVA-FRCC mixed with aeolian sand was established. The calculated values of the model were in good agreement with the experimental values.
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Influence of multiple factors on flocculent structure and rheological properties of cement slurry

LIU Chang-qi, LIU Hao-jie, SU Lei, BAI Ji-wen, LIU Li-dong, TIAN Jiawei

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The rheological properties is an important basis for the design of grouting parameters in geological disaster management. Rheological property of cement suspension is affected by many factors, and its mechanism is uncharted. In this study, the influence of particle size distribution on rheological property is analyzed. The focused beam reflectivity measurement system was used to measure the chord size and number of flocculated particles under different water-cement ratio, cement fineness and shear rate, and the rheological properties of slurry under the same conditions were measured. The effects of particle size distribution on rheological properties were analyzed. The results show that with the increase of water-cement ratio, cement fineness and shear rate, the chord size of flocculated particles decreases and the number of particles increases. The degree of particle flocculation increased linearly with the increase of time. The yield strength and molding viscosity decrease with the increase of water-cement ratio, and increase with the increase of cement fineness. The apparent viscosity decreases with the increase of shear rate and shows a reversible change. The change of flocculation structure is consistent with the change of rheological properties. The water-cement ratio, cement fineness and shear rate affect the rheological properties by influencing the flocculation structure. This study reveals the change of rheological properties from the perspective of flocculation structure, which can provide guidance for the design and application of cement grout.
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Study on the influence of filling concrete on the axial tensile performance of steel tube inner and outer flange joints

LIU Yongsheng, Wang Hao, TAO Xin, Lin Gang, Zhang Chuanjin, Wang Qiulin

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Steel tube inner and outer flange joints are widely used in large-span transmission towers. Filling concrete in chord has become an effective method to improve the bearing capacity and the stress on steel tubes. In order to reveal the influence of filled-concrete on the mechanical properties of steel tube inner and outer flange joints under axial tensile load, two concrete-filled inner and outer flange joints (CFIOF) and two inner and outer flange joints (IOF) were designed for axial tensile tests. The failure mode, flange opening deformation, strain development of key parts and axial tension ratio β of outer and inner bolts were compared and analyzed. Then, a CFIOF finite element model was established and validated for parameter analysis to reveal the influence of flange thickness, bolt spacing, and concrete strength on β. The study found that the failure mode of CFIOF is basically the same as that of IOF, both of which are flange plate opening, accompanied by deformation of the bolt thread area. When the opening deformation is the same, the bearing capacity can be increased by more than 5%. Filling concrete can make the inner and outer bolts more uniformly under stress. As the thickness of the flange plate increases, β shows a trend of first increasing and then decreasing, gradually approaching one. With the increase of bolt spacing and concrete strength, β decreases gradually and tends to 1. The effect of concrete strength on β is the smallest.
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Influence of Control Stability of Construction Parameters on Surface Settlement Induced by Shield Tunneling in Soft Soil

hehaini, zhangrongjun, yangdong, taofengjuan, zhengjunjie

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In the researches on surface settlement induced by shield tunneling, most of the construction parameters are regarded as deterministic values, ignoring their variability during the control process. This paper aims to investigate the relationship between the control stability of construction parameters control and the surface settlement caused by shield tunneling. Based on the shield tunneling project of a certain section of Wuhan Metro Line 2, a three-dimensional numerical model is established to simulate the whole process of shield tunneling. The influence of the variation level of chamber earth pressure, over-excavation gap, and grouting pressure on the surface settlement is investigated. An effort is also made to gain insight into the influence area of different construction parameters. The results show that the control stability of construction parameters control during the shield tunneling process has a great influence on the surface settlement, and the dispersion degree of surface settlement is positively correlated with the variation level of construction parameters. Moreover, the uncertain surface settlement is affected by the control stability of construction parameters within the primary impact area. According to the numerical analyses, the control standards for the coefficient of variation of the construction parameters were obtained. The research results provide a reference for the construction control and risk assessment of shield tunnel engineering.
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Development and application of particle-scale tensile strength testing system for biocemented bond

Yan Jiang, Wu Huanran, Xiao Yang, Liu Hanlong

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Biocementation technology is an emerging eco-friendly cementation technology that utilizes the metabolic activity of microorganisms to cement geomaterials. The particle-scale studies on the strength of biocemented bonds remain rare, although extensive research have been conducted on the mechanical properties of biocemented bonds at the element or field scale. Traditional geotechnical testing equipment is insufficient for accurately measuring the strength of biocemented bonds at the particle scale. To precisely measure the mechanical properties of biocemented bonds at the particle scale, a particle-scale tensile testing system for biocemented bonds was developed and the tensile strength tests for particle-scale biocemented bonds was carried out with this system. This testing system was comprised of a displacement control module, a tension measurement module, a specimen fixing module, and an imaging observation and recording module. The displacement control module ensures the stable operation of the loading stage, while the tension measurement module accurately measures and records the evolution of tensile force. The specimen fixing module securely holds specimens to prevent slippage or misalignment. The imaging observation and recording module captures and records the failure behavior of the specimen during the tensile process in real time. Detailed descriptions of specimen preparation, the testing process, and tensile test results were provided. The test results demonstrate that the testing system exhibits high precision and excellent stability. It effectively measures the tensile strength and clearly captures the failure characteristics of biocemented bonds upon tensile loading, providing reliable experimental system for the study of the mechanical properties of biocemented geomaterials.
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Mechanical properties and microstructural analysis of lignin fibler-lime composite expansive soils

LIU Haotong, WANG Yejiao, WANG Taian, GUO Zhaomin

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Expansive soil is a typically problematic soil that exhibits the engineering characteristics of swelling and shrinkage. It is highly sensitive to climatic changes, often leading to engineering disasters such as slope instability and landslides. While traditional inorganic chemical modifiers (such as lime, cement, etc.) can effectively improve soil strength, these modifiers are associated with environmental issues, particularly high carbon emissions. This study investigated the use of a novel green, low-carbon material—lignin fiber (LF)—for the modification of expansive soil. Unconfined compressive strength test, direct shear test, free swell test, mercury intrusion porosimetry, and scanning electron microscope were performed to analyze the mechanical properties of lignin fiber improved expansive soil. The effects of modifier dosage and curing age on the mechanical properties and microstructure of lignin fiber-lime composite-treated soil were also studied. The results indicated that 8% lignin fiber significantly improved both the shear and compressive strengths of expansive soil. After the optimal treatment, the mechanical properties of the composite improved soil were comparable to those of 4% lime-treated soil. Lignin fiber can effectively enhance the micro-structure of expansive soil by enhancing the bonds among soil particles. The results illustrated that lignin fiber, as a new low-carbon material, can significantly improve the engineering properties of expansive soil, to partially replace or reduce the use of traditional modifiers in the field of soil improvement.
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Study on the Mechanical Response Characteristics of Surrounding Rock during In-Situ Excavation of Large-Section Tunnel

mazhiguo, liulei, songwenming, zhaoyingai, daiyiming, lvxiangfeng

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The in-situ excavation process of large-section highway tunnels causes significant disturbance to the surrounding rock and poses high construction risks. However, research on the mechanical characteristics of the surrounding rock during in-situ excavation of tunnels is still limited. This paper investigates the mechanical characteristics of surrounding rock under different excavation methods using physical model experiments and a simplified stress model. The results of the tunnel excavation physical model test show that the displacement variation is the largest in the single-sided borehole excavation method, the surrounding rock pressure accumulates at the arch shoulder in the single-sided step excavation method, and the displacement is the smallest with a more uniform surrounding rock pressure distribution in the single-sided CD excavation method. The simplified model analysis of surrounding rock stress indicates that the displacement at the arch foot is larger than at the crown, and the greater the damage degree of the surrounding rock, the larger the displacement. Field measurements confirm that model test values of rock pressure and displacement align closely with measured values, showing similar displacement trends. When the damage coefficient D is 0.2, model values under both methods accurately reflect the measurements. Moreover, the single-sided CD method is more favorable for long-term rock stability. These findings provide theoretical guidance for similar large-section tunnel projects.
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The influence of stiffeners on the stress performance of transition nodes of tree shaped column cover plates with irregular steel pipes

xujinmeng, xionggang, xieqiang

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The construction of irregular steel pipe tree shaped column nodes is complex, and the use of cover plates to connect the trunk and branches can greatly reduce the difficulty of construction. Understanding the influence of cover plate stiffeners on the mechanical properties of such nodes is of great significance for guiding the design of similar projects. This article takes the special-shaped steel pipe tree column at Chongqing East Station as an example, and conducts scaled tests on two nodes with or without stiffeners to study the influence of stiffeners on key indicators such as force transmission mechanism, stress distribution and level, node failure mode, and node bearing capacity in the node area of the special-shaped steel pipe tree column. The research results indicate that the stiffness of the cover plate is greatly improved after the installation of stiffeners; After setting the stiffeners, the stress distribution in the node area, especially in the cover plate, tends to flatten and the peak stress decreases; Similar to nodes without stiffeners, in the later stage of loading, nodes with stiffeners experienced strength and local instability failure at the roots of the branches. However, with stiffeners, the degree of local bulging of the cover plate and node area trunk was significantly reduced; The bearing capacity of the node is significantly improved after the installation of stiffeners.
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Research progress on recycling and utilization of brick-concrete

Jiao Yang, Fang Xiangwei, Shen Chun-ni, Tian Jing, Huang Sheng, Jiang Wen-chen

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The iterative renewal of the brick-concrete structure will produce a large amount of brick-concrete construction waste, and the resource utilization of brick-concrete construction waste can effectively solve the shortage of natural sand and gravel resources as well as alleviate the harm of construction waste landfill. The brick-concrete recycled materials are divided into three categories according to the particle size: brick recycled coarse aggregate, fine aggregate and powder. Brick-concrete recycled coarse aggregate can be used as aggregate for recycled concrete and base course of road base project; recycled fine aggregate is often used in recycled mortar, recycled blocks and improved performance of soil /cured soil and so on. The chemical composition of brick-concrete recycled powder is similar to cement, lime powder, fly ash, etc., which can be used as cementitious materials through ion exchange, generation of expanded substances, pozzolanic reaction and crystallization, etc.; Waste brick recycled powder has good pozzolanic activity, which can be used as raw materials for the preparation of waste brick recycled powder base polymer cementitious materials through alkali excitation, which has good fluidity, mechanical properties and high-temperature performance, and the reaction mechanism mainly includes Si, Al monomer dissolution, monomer reconstruction, polycondensation and filling cementation. Brick-concrete recycled materials in the future should improve the performance of renewable raw materials, expansion of application way, mechanical properties and curing mechanism, disposal and application standards development and other aspects of in-depth research.
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A CNN-LSTM structural strain response prediction method based on feature selection

Wang Wei, JIANG SHAN, HU JIANXIU, LU GUOYUN

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During the long-term service of a building structure, various external and internal factors can lead to the failure of key components. The structural strain response serves as an intuitive indicator of the operational status of these components. Therefore, accurately predicting the structural strain response is crucial for the long-term monitoring of building structures. In this paper, we propose a CNN-LSTM-based method for predicting structural strain responses, enhanced through feature selection, and validate it using measured data from the health monitoring system of the Pearl Tower in Northern Xinjiang. The input model’s features are determined through Pearson correlation analysis, and their importance is ranked and selected using the random forest algorithm. We developed a CNN-LSTM structural strain response prediction model and applied the Bayesian optimization algorithm to fine-tune the model’s hyperparameters, thereby enhancing its prediction accuracy. We then compared the prediction results with those obtained from conventional LSTM and BiLSTM models. The results demonstrate that the correlation coefficients between the predicted and actual values of the CNN-LSTM model at all strain measurement points exceed 0.99. This indicates the model’s superior performance in predicting the strain response of components, as well as its higher prediction accuracy compared to the LSTM and BiLSTM models.
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Experimental study on the effect of sodium silicate enhanced microbial grouting reinforcement

SHANG Zhiyang, PENG Jie, Renjie Wei, Liangliang Li, Zhao Jiang, DI Dai

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Microbially induced calcium carbonate precipitation (MICP) technology has broad application value and potential in improving the mechanical properties of rock and soil. However, this method still has defects, such as low efficiency and long reinforcement periods. An appropriate amount of sodium silicate was added to the bacterial solution to enhance the efficiency of MICP reinforcement and shorten the reinforcement period based on conventional MICP. The solution tests and sand column tests were carried out, as well as the macro and micro detection tests. The enhancement effect and mechanism of sodium silicate on microbial sand fixation were studied. The results show that the bacterial activity increased by about 14 % and the amount of calcium carbonate in the sand column increased by about 7 % after adding appropriate amount of sodium silicate, and the MICP reinforcement efficiency and sample uniformity were enhanced. After 2 times of sand column reinforcement, the sample can be formed. After 10 times of reinforcement, the compressive strength of the sample is about 5.9 MPa, which is about seven times higher than that of the control group. Microscopic detection tests show that after adding sodium silicate, the hydrated calcium silicate gel generated in the environment can play a role in filling sand pores and cemented sand particles, thereby improving the strength and reinforcement efficiency of the sample. This method can provide theoretical guidance for popularising and applying microbial sand fixation.
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Adaptive elimination method for time-lag effects in thermal displacement monitoring data of long-span bridges

LONG Wei, SHEN Anbin, WANG Shengli, WANG Yao, DUAN Lingling, ZHOU Guangdong

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The elimination of time-lag effects is a crucial step in enhancing the correlation between thermal displacement and temperature of long-span bridges, and improving the reliability of displacement-based structural operation damage identification. The fixed time translation method cannot capture the changes in time lags over time and is difficult to completely eliminate time-lag effects. This article uses functional data analysis methods to transform the elimination of time-lag effects into finding an optimal warping function to align thermal displacement and temperature, and proposes an adaptive elimination method for time-lag effects in thermal displacement monitoring data. Firstly, the mechanism of time-lag effects was revealed through numerical simulation. Secondly, an adaptive elimination method for time-lag effects based on phase-amplitude separation of functional data was introduced. Thirdly, the effectiveness of this method was verified using long-term monitoring data of expansion joint displacement and temperature of a large-span rail-cum-road bridge. Finally, a strategy was presented to cope with the end effect of the adaptive elimination method. The research results indicate that the thermal inertia effect formed by low thermal conductivity is the intrinsic reason for the generation of time-lag effects. The adaptive elimination method of time-lag effects can automatically find the optimal warping function for time-lag effects elimination according to the degree of time lags. The proposed method is significantly better than the fixed time translation method. The strategy of data extension can effectively remove the end effect and achieve complete elimination of time-lag effects.
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Deformation characteristics and its ideal elastic-plastic model of fine-grained sulfate salted soil in Qinghai

ZHANG Xinmiao, ZHANG Wen, ZHANG Ning, WANG Longxuan, YANG Miao

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This paper conducts an in-depth study on the deformation characteristics of sulfate salted soil in the Qinghai region and proposes an ideal elastoplastic model that considers salt content and confining pressure. Firstly, through the determination of liquid plastic limit and soluble salts, it is indicated that the four typical areas are primarily composed of silty clay and clay, with sulfates being predominant. Original saline soil samples from three sampling points were selected and subjected to artificial salt washing, preparing six soil samples with different mass ratios of sodium sulfate. Secondly, consolidation undrained triaxial tests were conducted under four confining pressures and six salt contents, revealing that the stress-strain relationship of the saline soil exhibits a distinct ideal elastoplastic characteristic: a clear linear segment is visible before yielding, with no significant hardening or softening after yielding. Under the same confining pressure, the initial elastic modulus, yield stress, and shear strength all gradually decrease with increasing salt content; at the same salt content, the initial elastic modulus and yield stress increase with increasing confining pressure. Finally, based on the test phenomena, the constant initial modulus and yield point in the ideal elastoplastic model are considered as functional expressions. By using MATLAB programming analysis and parameter optimization, a model is established where the initial modulus and yield stress are linearly expressed in terms of confining pressure and salt content. This model has fewer parameters and, in addition to reflecting changes in strength, can also describe the influence of salt content and confining pressure on the initial modulus, thus providing a more accurate description of deformation for engineering reference.
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Effects of moisture content and foam injection ratio on mechanical properties of high viscosity mudstone with soil pressure equilibrium shield

Feng Lin, Zou Kunmi, Liu Guijun, Tang Weixiang, He Qihai, Zhang Wengang, Yang Yang, Sun Weixin, Yang Wenyu

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The problems of difficult spoil discharge and cutterhead mudding pose many challenges to the advancement of earth pressure balance (EPB) shield tunneling, especially for high-viscosity shale strata, where spoil improvement is necessary. Relying on the shield tunneling project of Shuan Tunnel (Sichuan section) of Chengdu-Chongqing Central Line, foam performance evaluation, vane shear test, interface shear test, and indoor shield tunneling model tests were carried out on shale to explore the optimal concentration range of foaming agent, and the effects of water content and foam injection ratio on the normal interface force, longitudinal interface force, and cutterhead mudding were investigated. The results show that: (1) The optimal volume fraction of the foaming agent is around 3%, with the corresponding foam expansion ratio and half-life being 29.1 and 8.71 min, respectively. (2) Based on the above optimal volume fraction, with the increase of water content and foam mass ratio, the vane shear strength, direct shear strength, cohesion, internal friction angle of shale, the average pressure of jacks, and the torque under the action of unit jack pressure all decrease to varying degrees. The adhesion amount of spoil on the shield cutterhead does not change significantly, but the consistency of shale decreases, and the cutterhead mudding is improved. (3) Overall, the average advancement speed increases. The greater the average pressure of the jacks, the greater the cutterhead torque. The improvement effect of the foaming agent on shield tunneling is better than that of water content. The research results have certain reference significance for evaluating the construction of EPB shield tunneling in high-viscosity shale strata.
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Research on characterization of rock joint surface roughness and strength prediction method considering sampling spacing

shizhenning, baodewei, wangzihang, zhujian, zengshiyang

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The roughness of rock joint surfaces is the most important factor in determining their shear strength. Currently, the roughness of rock joint surfaces is mostly expressed using the root mean square slope (Z2) value, which is closely related to the sampling interval in the process of digitizing joint surfaces. To further improve the calculation accuracy of rock joint surface roughness, this paper conducted research on the characterization and strength prediction methods of rock joint surface roughness considering sampling interval. The main research results are as follows: First, the roughness of joint surfaces varies among different types of rocks after splitting, with granite exhibiting the highest roughness, followed by quartzite, and then red sandstone and mudstone. Second, the Z2 values of different joint surface contour lines show a linear decrease with the increase of sampling interval. And the greater the fluctuation of the joint surface, the more obvious the influence of sampling interval on Z2 value. A calculation formula for the joint surface roughness coefficient, which considers the sampling interval, was established based on a logarithmic function. This new formula offers clearer physical meaning and higher prediction accuracy compared to the original JRC prediction model.
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3D geological modeling of karst mountainous areas and its application in 3D evaluation of tunnel planning

weilai, caocong, liuzhi, gongsiyu, xiehuijun, lixingru

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The geological environment in karst regions is inherently fragile, necessitating a suitability assessment for tunnel planning to mitigate geological issues induced by construction activities. A pressing challenge is to develop a detailed three-dimensional geological model in karst mountainous areas, which can serve as the foundation for conducting a comprehensive 3D suitability evaluation for tunnel planning.This study focuses on the Liangjiang segment of Zhongliang Mountain in Chongqing as the research area. Employing geological modeling methods and grid subdivision techniques tailored to the regional geological characteristics, a series of detailed 3D geological and attribute models have been constructed. Based on the Analytic Hierarchy Process (AHP) and a multi-level index overlay method, a 3D evaluation system for tunnel planning has been established, aligned with the local geological conditions and the current state of tunnel construction. Furthermore, the 3D evaluation results have been utilized for tunnel planning assessment and analytical applications.The findings indicate that by employing appropriate 3D modeling methods, one can construct detailed geological models in karst mountainous regions. This serves as a foundational data source and spatial analysis framework, enabling the establishment of a 3D suitability evaluation system for tunnel planning that is consistent with the local geological environment. The results provide substantial support for the planning and site selection of tunnels in karst mountainous areas and the optimization of underground space patterns in mountainous cities.
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Experimental study of multifaceted solid waste synergistic treatment based on harmlessness and resource utilization of red mud

YAN Lijun, YANG Junjie, WU Yalei, LI Fengmin

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Red mud is a kind of solid waste in the production process of aluminum industry. In order to solve the waste of land resources and environmental pollution and resource utilization problems caused by long-term stockpiling, this paper adopts CGFPA curing agent with calcium carbide residue, ground granulated blast furnace slag, fly ash, phosphogypsum and graphene as components for the harmless treatment of red mud. Tests of unconfined compressive strength, acidity and alkalinity, and toxicity leaching were used to study the effects of curing agent dosing, total initial moisture content, and curing age on the strength properties, acidity and alkalinity, and toxicity leaching properties of solidified/stabilized red mud. The results show that the unconfined compressive strength of solidified/stabilized red mud increases and then decreases, while the pollutant concentration decreases and then increases, there exists an optimal total water content ratio (the ratio of the total initial water content to the liquid limit of the red mud) with the maximum strength and the lowest pollutant concentration, and that the optimal water content ratio increases linearly with the mixing ratio of the binder. The optimal water content ratios are 1.0, 1.2, 1.3, and 1.4 for 15%, 20%, 25%, and 30% mixing ratios, respectively, corresponding to the optimal total initial water content of 37.8%, 45.4%, 49.1%, and 52.9%, respectively. The pH value of the solidified/stabilized red mud decreased with the increase of the curing age, and was lower than 9.5 after 90ds; it decreased with the increase of the total water content ratio, and gradually tended to be stabilized. In addition, the concentration of pollutants in the solidified/stabilized red mud decreased gradually with the increase of binder mixing ratio, and the removal rate of seven pollutants could reach more than 80% when the mixing ratio was 30% and the total water content ratio was 1.4. The research results have certain practical significance for the harmless treatment and resource utilization of red mud.
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Machine learning investigates the overlooked organic excitation effects in the UV/PS system by UV185

LUO Jingyao, ZHEN Peng, LIU Yudan, LIANG Jialiang

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The accelerated degradation of pollutants in the vacuum ultraviolet/persulfate (VUV/PS) system is often attributed to the effective excitation of H2O and persulfate (PS) by UV185. However, the direct excitation of pollutants by UV185 has been largely overlooked, which may result in an underestimation of UV185's role in pollutant degradation. To address this gap, this study integrates machine learning and density functional theory (DFT) calculations to elucidate the mechanism of UV185 in the VUV/PS system through a data-driven approach. Initially, the ground-state and excited-state molecular descriptors for 30 types of organic pollutants were derived via DFT calculations and used as input parameters. Subsequently, a stochastic forest model was employed to predict the degradation kinetic constants and mineralization rates of pollutants in various systems, serving as output parameters. By evaluating the model's performance under different input conditions, molecular descriptors with high relevance to the output parameters were identified and retained. Ultimately, the most influential input parameters in each model were analyzed using the Shapley Additive Explanation (SHAP) method, which facilitated the speculation of the reaction mechanism. The findings revealed that, compared to the UV system, the contribution of S1 excited state descriptors and nucleophilic reaction-related descriptors in the VUV system was markedly enhanced, suggesting that UV185 promotes the transition of pollutants to a more reactive S1 state, thereby accelerating their degradation and mineralization through enhanced photolysis and nucleophilic reaction pathways.
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Enhancement Mechanism of Biomass Fbire on Filter Cake Formation for Slurry Shield Tunnelling in Sandy Ground

XU TAO, SHI JINQUAN, DING ZHI

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In the highly permeable soil, pure bentonite slurry is hard to form a filter cake at the tunnel face during slurry shield tunnelling. The viscosity of polymer modified slurry is too high and it may pollute the environment. The enhancement mechanism of biomass straw fiber on the filter cake formation for bentonkte slurry during slurry shield tunnelling in saturated sandy soil was introduced. The infiltration process of slurry in saturated sandy soil was investigated using column infiltration test. The filtration loss, filter cake formation and effective pressure transfer were analysed. The effects of biomass fiber content on filter cake formation and effective pressure transfer were discussed. The results show that: (1) the viscosity of biomass fibre enhanced slurry is low, the stability of suspended particles is high and the density of biomass fibre enhanced slurry is low; (2) the ability to form a filter cake of the biomass fibre enhanced slurry is greatly improved, which can reduce the use of bentonite; (3) the infiltration model well predicts the infiltration process of biomass fiber enhanced slurry.
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Study of the Mechanical Behavior of the Cable-Saddle System of the Spatial Main Cable Suspension Bridge

TAN Zhengjun, Wang Lu, Gu Song, Shen Ruili, Bai Lunhua

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To clarify the mechanical behavior of the cable saddle system in spatial cable-stayed suspension bridges, based on the structural characteristics of two types of spatial cable saddles, a theory of lateral force synthesis was derived, and the force patterns of the two types of spatial cable saddles were demonstrated. Taking a certain spatial cable-stayed suspension bridge as an example, a slice numerical model was established using ABAQUS to study the internal wire force characteristics, lateral pressure distribution patterns, and friction resistance composition of the two types of spatial cable saddles. The results show that the force pattern of the inclined plane saddle is the same as that of the plane saddle, and the lateral forces between the saddles are all caused by radial forces pointing to the center of the circle; for the spatial curved cable saddle, the radial force is approximately equal to the vector sum of the radial forces produced by vertical and horizontal bending, and in the spatial curved cable saddle, the outer pressure is greater than the inner pressure; the internal stress of the saddle groove is mainly concentrated in the local contact area, which is consistent with the classical Hertz theory; the force chain between the upper and lower layers of wires forms a diamond shape, with the force value gradually increasing with depth, but there is a sharp drop at the bottom layer; in the inclined plane saddle, the saddle base provides 86.4% of the friction resistance, and the saddle side only accounts for 13.6%; in contrast, the base of the spatial curved cable saddle provides 86.62%, and the saddle side provides 13.38%. In both types of spatial cable saddles, the contribution of the saddle base to friction resistance is much greater than that of the side.
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Study of Large-scale direct shear test on shear characteristics for MICP-treated soil using biostimulation approach

LIU Aqiang, XIE Liuyang, XIAO Yang, HUANG Xiaoli, GAO Yiming, GOU Ruinan, CUI Hao

Abstract: (226) HTML (0) PDF (0.00 ByteKB) (0)

Microbially induced calcium carbonate precipitation is a new and sustainable technology, which includes bioaugmentation and biostimulation approaches. However, the existing related research is mostly limited to bioaugmentation approach, and there is relatively little research on biostimulation approach, especially large-scale experiments. In this study, the surface soil along Jialing River in Chongqing is taken as the research object, and the influence of different reinforcement degrees on the shear characteristics of large-scale samples is explored based on biostimulation approach. In addition, the distribution of calcium carbonate content in different directions was also determined. The results show that the stress-strain relationship of the specimen before and after strengthening has changed from strain hardening to brittle fracture and strain softening. In terms of dilatancy, the specimen shows a phenomenon of shear shrinkage before reinforcement, while the specimen shows a slight shear shrinkage first and then a phenomenon of shear expansion after reinforcement. After reinforcement, the shear strength of the specimen has been greatly improved. The calcium carbonate content in the sample decreases with the increase of the distance from the top surface of the sample, and the calcium carbonate content in the sample presents a distribution pattern of high in periphery part and low in middle part. The results of this study can provide reference for the application of biostimulation approach in field tests.
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Analysis method for bending capacity of core-filled composite pipe pile

YU Xuekui, XIAO Shiguo, WU Bing, LIANG Yao

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The core-filled composite pipe pile is composed of the prestressed high-intensity concrete pipe pile (PHC pile) and ordinary reinforced concrete inside it, which can be helpful to enhance the bending resistance of the pipe pile. For the new composite pile, the calculation formula of the total bending capacity is derived according to static equilibrium conditions of the pile cross-section. Based on the strain difference at the interface between the inner circular and outer ring areas of the pile, the equivalent rectangular stress diagram coefficients in the current specification suitable for rectangular cross-section are improved. So, the computation method of the stress diagram coefficients suitable for the composite pile with circular cross-section are established. The research results show that the results obtained using the proposed theoretical formula agree well with the tests. The pile bending capacity is obviously influenced by the inner reinforcement ratio and tension stress on the prestressed reinforcements. The bending capacity increases nonlinearly with the reinforcement ratio and decreases linearly with the increase of the tension stress. The sensitivity of the bending capacity to main factors follows the order: outer diameter > outer reinforcement ratio >ring thickness > inner reinforcement ratio > tension stress. The core filling can improve the pile bending capacity by 26% and 68% under the inner reinforcement ratio 1% and 3%, respectively. The reason for reinforcing effect of core filling is that the filling can strengthen the limit state and reduce the height of neutral axis on the cross-section, which leads to the significant increase of the bending resistance ratio of the outer ring up to 73%~83%.
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Calculation method for shear bearing capacity of double T-shaped steel-concrete composite beams

CHEN Jianbing, TIAN Zhuangyan, LIU Cong, LI Xiang

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In order to investigate the shear resistance performance of double-T-shaped steel-concrete composite beams (DTSCB), three DTSCB specimens were designed and manufactured with concrete slab width and steel plate thickness as parameters, based on the test results of shear-mid-span deflection curve, shear-relative slip curve and strain distribution, The influence of structural parameters on the bearing capacity and deformation capacity of the composite beam was studied. An ABAQUS finite element model was established and validated by comparing with the experimental results to verify the accuracy of the model. The influence of different shear span ratios on the shear resistance of the steel beam, concrete slab, and wing plate with different structural parameters was simulated, and an expression for shear resistance was established. The results show that the limit shear span ratios for diagonal compression failure, shear failure, and bending failure of the composite beam are 1 and 3, respectively. When the shear span ratio is 1-3, the steel plate takes up about 70% of the shear resistance. The accuracy of the shear resistance calculation formula established is higher than that of the current code.
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Image segmentation approach for surface rust of existing steel structures based on improved DeepLabV3+

MENG Qingcheng, ZHANG Fa, XIONG Shuang, QI Xin

Abstract: (227) HTML (0) PDF (0.00 ByteKB) (0)

Surface corrosion constitutes a prevalent defect form in steel structures, which can undermine the section of components and deteriorate their mechanical properties. Thus, it is imperative to monitor and assess the corrosion damage of steel structures. A lightweight semantic segmentation model for rust images, based on HL-DeepLabV3+, has been proposed to address the challenges of reading errors, texture misjudgments, and color discrepancies caused by visual fatigue during manual inspections. This model aims to improve segmentation accuracy while reducing the parameter count associated with traditional deep learning networks used in rust recognition. Firstly, the coding portion of the backbone network was replaced with a lightweight MobileNetV3 network to minimize the number of model parameters. Secondly, the strip pool module and pyramid pool module were incorporated into the void space pyramid pool module, enabling the network to capture the long-range dependence of isolated rust regions and eliminate the interference in the background region. Finally, the attention mechanism was introduced to make the network focus more on the pixel region that plays a decisive role in rust classification and enhance the feature expression ability of rust. The test results indicate that: Compared with the original model, the size of the HL-DeepLabV3+ model is reduced by 66.73%, and the Accuracy, mIoU, MPA, and F1 scores are increased by 2.54%, 10.11%, 6.79%, and 6.15% respectively. Moreover, the effect is superior to the classical UNet, FCN, SegNet, and DeepLabV3+ semantic segmentation models. This not only realizes the lightweight of the model but also enhances the segmentation accuracy of rust damage.
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Analysis of Lateral Load Bearing Performance of Pile Foundations Considering Pile Installation and Consolidation Effects

liuwuhao, zhangfujin, lihui, caoxue, jingqingxin, dongjunjie, yijiangtao

Abstract: (201) HTML (0) PDF (0.00 ByteKB) (0)

In ocean engineering, large-diameter steel pipe piles are commonly used as foundations, and they are often installed using either hammer driving or static pressing methods.In cohesive soil foundations, the soil displacement and heave caused by the pile driving effect weaken the shear strength of the surrounding soil and generate excess pore pressure. After pile installation, the excess pore pressure around the pile gradually dissipates, and the soil undergoes reconsolidation, with its strength and stress state gradually recovering. However, existing studies and design codes rarely consider the effects of pile driving and consolidation on the bearing performance of horizontally loaded piles.This study uses a self-developed multi-stage Euler-Lagrange method to continuously and comprehensively simulate three distinct stages of static-pressed pile installation: pile penetration, consolidation strengthening, and horizontal loading. The research delves into the pile-soil interaction mechanism, the soil strength recovery mechanism between piles, the ultimate resistance of the soil around the pile, and the variation of the P-y curve. The results show that while the consolidation effect does not change the soil deformation mechanism, it significantly increases the ultimate soil resistance along the pile side. Furthermore, the study clearly identifies and quantifies the effects of pile driving and consolidation on the bearing capacity of horizontally loaded piles, establishing a model for the growth ratio of ultimate soil resistance with depth, and proposing a P-y curve that incorporates both pile driving and consolidation effects. The research findings have significant theoretical value and practical implications for optimizing the calculation methods for the static bearing capacity of marine pile foundations.
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Analysis of Vibration Propagation and Influencing Parameters in Dynamic Compaction of Miscellaneous Fill Slope

Zhu Jianmin, Dong Baozhi, Yu Yongtang, Zheng Jianguo, Wen Yukun

Abstract: (307) HTML (0) PDF (0.00 ByteKB) (0)

The influence of three independent factors, i.e.vibration source distance, tamping energy and tamping settlement, on the vibration velocity under the energy levels of 4000kN · m, 12000kN · m and 25000kN · m was compared and analyzed in the miscellaneous fill slope and flat site. On this basis, the Bp neural network and Sobol sensitivity analysis method were used to analyze the influence of the above three factors on the vibration velocity. The results indicate that in slope sites, vibration velocity follows a negative exponential relationship from the slope’s shoulder to its base. An "energy concentration" effect is observed at the slope's shoulder, where the vibration velocity is higher than that of flat sites at the same source distance. In miscellaneous fill slopes, vibration velocity mostly ranges between 4 and 25 mm/s, and though it also follows a negative exponential relationship with impact energy, the effect of energy on vibration velocity is limited. As tamping settlement increases, vibration velocity initially rises rapidly, then slows, eventually stabilizing. After reaching a "concave" inflection point on the cumulative tamping curve, the velocity increases or the growth rate accelerates; beyond a "convex" inflection point, the velocity decreases or the growth rate slows. Sensitivity analysis shows that tamping settlement has the greatest influence on vibration velocity, being 1.55 times more significant than source distance and 5.93 times more significant than tamping energy. Reducing tamping settlement is the most effective way to lower vibration, followed by increasing source distance, with tamping energy having the smallest effect.
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Effect of partial leakage during deep excavation in water-rich sandy strata on retaining wall deformation and ground settlement

QIU Mingming, Li Xiaomin, ZHAO Haifeng, DUAN Junyi, Yang Guolin

Abstract: (180) HTML (0) PDF (0.00 ByteKB) (0)

The stable and controllable deformation of deep foundation pit in water-rich sandy strata was the basic guarantee of underground engineering construction safety. Aiming at the leakage disaster of deep foundation pit in water-rich sandy strata, this paper takes the leakage incidents of launch shaft pit of subway station as the research background, summarizes and analyzes the development process and accident causes of water and sand leakage disaster through field investigation and survey data review, the characteristics of horizontal displacement of retaining wall, ground settlement behind wall and change of groundwater level outside the pit during partial leakage were systematically studied, and the effect rules of partial leakage on the deformation behavior of foundation pit were revealed by numerical simulation method. The results of research shows that the horizontal displacement of the retaining wall increases significantly due to partial leakage, and the maximum horizontal displacement of retaining wall after leakage is 1.29 to 1.47 times that before leakage. The ground settlement trough of sensitive zone deepens and widens due to partial leakage, and the maximum ground settlement after leakage is 1.16 to 2.67 times of that before leakage. The characteristics of "jump" fluctuation of groundwater level can be used as an important criterion for the precursor of leakage disaster in foundation pit. The combined treatment measures of grouting and high pressure rotating spouting pile can effectively deal with the problem of leakage disaster control of foundation pit in water-rich sandy strata.
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Study on the Mechanical Characteristics of Polyurethane Materials for Emergency Road Recovery under Cyclic Loading

XU Xiaoliang, Liao Wenjie, XU jiapeng, LI Bei, TAN Yizhong

Abstract: (117) HTML (0) PDF (0.00 ByteKB) (0)

Polyurethane foam material, with its rapid expansion, high strength, lightweight, and water-repellent characteristics, has significant engineering value in temporary repair works such as emergency road clearance after water damage. To study the mechanical characteristics of polyurethane materials for subgrade under cyclic loading, axial cyclic loading and unloading compression test , and tangential cyclic shear test were carried out on polyurethane samples containing interface, and the change rule of stress-strain law and macro and micro damage characteristics of polyurethane samples wereanalyzed under different loading frequencies and loading ranges. The results show that: The strain of polyurethane samples increases and then decreases with the frequency of axial loading, and continuously increases with the upper limit of axial stress loading (up to 7%~8%); the maximum strain increment induced by axial stress loading is four times the corresponding value for the loading frequency, which has a more significant effect on the sample strain; under axial cyclic loading and unloading, the sample is mainly subjected to compression-shear damage along the cemented surface and tensile-shear damage along the vertical fissure-cohesive surface, the increase in the loading range of the tangential force causes a significant increase in the deformation of sample (up to 5%~6%), and eventually compression-shear damage along the cemented surface occurs; increase a certain amount of axial force (should not exceed 90% of the uniaxial compressive strength) can be better compaction of polyurethane materials, which can improve its shear performance, in engineering applications, it is advisable to avoid placing polyurethane materials in a cyclic shear stress state when the axial force is small or there is no loading.
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Experimental study of transparent soil modelling of pipe-soil interaction during uplift of rectangular pipe gallery

wuyuhan, qigeping, tangyuteng

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As a type of non-circular section corridor in the construction of underground comprehensive pipe corridors, the uplift process of rectangular pipe corridors has a more complex impact on the surrounding soil compared to traditional circular corridors. However, there is currently limited research on the pipe-soil interaction during the uplift process of rectangular pipe corridors. To address this issue, a transparent soil model test was conducted to study the pipe-soil interaction during the uplift process of rectangular pipe corridors. The focus was on measuring and analyzing the changes in the p-y curves of the rectangular pipe corridors at different densities and burial depths, as well as the displacement field changes of the surrounding soil. The research findings indicate that the p-y curve trends at different burial depths of the rectangular pipe corridor exhibit similar characteristics under varying densities, going through phases of linear increase, peak variation, rapid decline, and gradual decrease. The greater the density and burial depth of the rectangular pipe corridor, the larger the amplitude of change and the maximum bearing capacity. The displacement field changes of the soil at the same burial depth during different stages of the uplift process are similar, with the surrounding soil displacement transitioning from an overall upward movement to localized upward movement at the upper and lower sections of the corridor while the surrounding areas move downward. Additionally, at the same density and burial depth, the angle of the displacement change surface of the soil increases with the height of uplift.
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Calculation and numerical simulation of pollutant accumulation in the controlled environment by circulating air system

PAN Wu-xuan, ZHANG Hui-jie, SONG Gao-ju, SONG Chong-fang, LEI Yong-gang, LIU Xiao-zhi

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The circulating air system can make full use of the re-transportation capacity of the air and reduce the total real-time emissions, which has become an important choice for industrial ventilation due to its energy-saving and emission reduction characteristics. However, there is a phenomenon of pollutant accumulation in the controlled environment of the circulating air system, and the research on the precise control of the accumulation of pollutants in the controlled environment and the proportion of circulating air is not perfect. In this study, a real-time calculation method for controlling pollutant accumulation in the environment by circulating air system was developed. Based on the intermittency of pollutant emission in the foundry industry, a method for calculating the proportion of circulating air under different process conditions was proposed, and the proportion range of circulating air was dynamically adjusted. The spatiotemporal distribution of pollutants in a controlled environment was studied by CFD discrete phase model (DPM). The results show that the average error between the simulation results and the theoretical calculated values at different times is within 15%, which is in good agreement. The circulating air system can effectively reduce the fresh air volume and the total real-time emission of the dust removal system; The upper limit of the concentration of pollutants in the environment controlled by the circulating air system is determined by the calculation of the intensity of the pollution source, the proportion of circulating air, and the filtration efficiency of the dust collector. In addition, through the dynamic characteristics of pollutant concentration changes under different circulating air ratios in the controlled environment, it is very important to select the appropriate circulating air ratio, which is very important to reduce the pollutant accumulation in the environment controlled by the circulating air system on the basis of energy saving.
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H-junction Incomplete Mixing Laws and Empirical Models Considering Multiple Factors

gaojinliang, likunyi, zhangjiawen, dongwenchao, yinxiaoming, zhengxiaoxin

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As an important component of water supply networks, the H-junctions exhibit unclear characteristics of income-flow incomplete mixing. This paper investigates the phenomena and influencing factors of incomplete mixing at H-junctions within water supply networks, intending to improve existing water quality simulation techniques. By combining computational fluid dynamics (CFD) numerical simulations and laboratory experiments, the effects of various factors such as pipe diameter, spacing of tees, and inlet and outlet Reynolds number ratios on incomplete mixing at H-junctions were explored. The findings suggested that while pipe diameter has minimal influence on mixing, spacing of tees and inlet/outlet Reynolds number ratios significantly affect the degree of mixing. Moreover, the experimental results aligned well with CFD simulations, validating their accuracy and providing data for establishing an empirical model for incomplete mixing at H-junctions under different spacings of tees. Ultimately, an empirical model for H-junction incomplete mixing based on the specific spacing of tees conditions was proposed. Selecting appropriate mixing models in practice to enhance the accuracy of water quality simulations in water supply networks was recommended, which is crucial for ensuring water safety and optimizing operational scheduling.
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Strength characteristics and environmental effects of red mud-based cementitious material activated with calcium carbide slag-phosphogypsum

LI Xiang, GUO Rongxin, LIU Zhuo

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The low hydration activity and high heavy metal ion content of red mud restrict its application in the field of building materials, and the preparation of good performance and economic and environmental friendly red mud-based cementitious material to realize the large admixture utilization of red mud is a problem to be solved in the green and efficient application of red mud. Red mud-based environmental cementitious material (RFCG) was prepared by activated red mud and fly ash with calcium carbide slag and phosphogypsum. The effects of calcium carbide-phosphogypsum ratio, calcination temperature of red mud, and sealing high-temperature curing time on the strength law of RFCG were investigated, and XRD, SEM-EDS, and ICP-OES were used to explain the strength law of RFCG from the microscopic mechanism and assess the environmental impact of RFCG. The results showed that OH- provided by calcium carbide slag promoted the reaction and generated C-(A)-S-H and a small amount of N-A-S-H gel, which contributed to the strength development of RFCG; AFt generated by SO42- provided by phosphogypsum enhanced the densification of the matrix by filling the microscopic pores to improve the strength, but the excessive AFt led to the development of microcracks in the matrix, which had an impact on the strength development greater. Calcination treatment enhanced the silica-aluminum ion leaching rate of red mud and attenuated the negative effect of organic matter in red mud, resulting in a substantial increase in the strength of RFCG. Conservation at 60 °C for 24 h effectively improved the early strength of RFCG. The prepared RFCG stabilized heavy metal ions, avoided secondary pollution to a certain extent, and could be applied in engineering fields such as pavement subgrade and mine filling.
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Research on the eccentric bending response characteristics of shield tunnel segments

HUANG Yingzhou, CHEN Wen, HE Qihai, WU Zhihao, YANG Yang, ZHANG Wengang, YANG Wenyu, SUN Weixin

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The flexural bearing capacity of shield tunnel segments is crucial for tunnel construction, as sufficient flexural bearing capacity ensures the overall stability and safety of tunnel engineering. Currently, there is insufficient research on the flexural bearing capacity of shield tunnel segments. This study employs a standardized method for detecting the bending capacity of shield tunnel segments, complemented by full-scale bending tests, to evaluate the bending capacity of segments in the Longgang shield section of the Shenzhen Shantou Railway. The effectiveness of the full-scale bending tests was verified using standard design calculation methods, and the bending capacity of the segments under eccentric compression was further analyzed through finite element numerical simulation methods. The results indicate that as the load is applied closer to the end of the shield tunnel segment, the pressure that the segment can withstand increases. The bending bearing capacity required at the center of the segment gradually decreases, while the bending bearing capacity required at the end initially increases and then decreases. When the ultimate bearing capacity that the segment can withstand under ideal conditions is applied to various eccentric working conditions, the displacement at the center of the segment gradually decreases, and the displacement at the endpoints shows a trend of initially increasing and then decreasing.
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Measurement and analysis of wheel-rail forces and vibration damping effects of steel-spring floating slab in soft-soil site

YE Junneng, SHENG Tao, BIAN Xuecheng

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In order to evaluate the influence of steel spring-floating plate track on wheel-rail forces and its actual vibration damping effects in a deep soft-soil tunnel, steel spring floating plate track bed and ordinary integral track bed were selected to meet the three preconditions of similar geological conditions, the same buried depth of the tunnel, and the same train speed and load. The vertical and lateral wheel-rail forces and rail deformation were tested respectively, and the three-direction vibration acceleration time travel curve of its rail, sleeper plate and tunnel wall, expand the time domain and frequency domain analysis. The results show that: (1) the floating plate can increase the vertical wheel-rail force slightly, increase the transverse wheel-rail force greatly, and make the low-frequency quasi-static action of wheel-rail force take a larger proportion; (2) The incensement of low-frequency components of wheel-rail forces cause the low-frequency jitter of the floating slab, resulting in a significant increase in rail displacement and volatility, and its vertical and lateral displacement increased by 2.4 times and 4 times respectively, which will have an adverse effect on smooth running; (3) The transverse and vertical vibration acceleration levels of the soft-soil tunnel wall were reduced by 5 dB, and the longitudinal vibration changed little, while the transverse and vertical vibration acceleration levels of the sleeper plate were increased by 10~12 dB, which proves that the floating plate effectively blocks the vibration energy. (4) The transverse and vertical resonance frequencies of the tunnel are about 50 Hz, and the floating slab effectively suppress the transverse and vertical vibration levels by 10~18 dB, satisfying the performance requirements of special vibration reduction measures. It shows that the increase of low frequency wheel-rail force has little effect on the high frequency vibration isolation performance of the floating slab, and the steel-spring floating slab is also appropriate to soft-soil subway tunnels.
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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

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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

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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

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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

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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: (170) 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: (364) 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

Abstract: (217) HTML (0) PDF (0.00 ByteKB) (0)

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

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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: (242) 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: (735) 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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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 48,2026 Issue 2

土木工程

Volume 48,2026 Issue 2

Environmental Engineering

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