Abstract:In-situ resource-based construction techniques can greatly reduce the cost of lunar surface base construction and guarantee high-quality operation and maintenance. How to make full use of in-situ resources to prepare high-performance building structural materials has become a hot research topic. In this study, geopolymers were prepared using lunar regolith simulant and reinforced with basalt fibers to enhance the mechanical properties of the materials.The effects of basalt fiber content on the failure modes and mechanical properties of lunar regolith simulant geopolymers activated by strong and weak alkali solutions were investigated. The results showed that the incorporation of basalt fibers changed the failure modes of lunar regolith simulant geopolymers and increased their deformation capacity. Under the condition of strong alkali solution activation, the optimal content of basalt fiber was 0.2%; while under weak alkali activation, the optimal content was 0.1%. The compressive and flexural strengths of the lunar regolith simulant geopolymers tended to increase and then decrease with the increase of fiber content. Compared with the strong alkali environment, the basalt fiber content had a more significant effect on the lunar regolith simulant geopolymers in the weak alkali environment.

Abstract:In order to study the cyclic shear characteristics of fiber-reinforced granitic residual soil, polypropylene fibers were mixed into the residual soil. The horizontal cyclic simple shear test of fiber-reinforced residual soil was carried out using a cyclic simple shear apparatus. The influence of different fiber contents (0%,0.3%, 0.6%, 0.9%) and cyclic stress ratios (0.15,0.20,0.25,0.30) on the dynamic characteristics of granitic residual soil was analyzed. The test results show that with the increase of cyclic stress ratio, the dynamic shear strain increases. The addition of fibers effectively restrained the development of dynamic shear strain of residual soil, and the higher the fiber content, the smaller the dynamic shear strain. Fibers increase the critical cyclic stress ratio of the residual soil. Under the critical cyclic stress ratio, the number of cycles at failure for reinforced samples is much greater than that for unreinforced ones. This indicates that the addition of fibers increased the toughness of the soil and greatly prolonged the failure time of the soil sample. Under the same cyclic stress ratio, the larger the fiber content, the greater the dynamic shear modulus and damping ratio. For the dynamic shear modulus, the smaller the cyclic stress ratio, the more obvious the advantage of fiber reinforcement. The improved H-D model can be used to analyze the dynamic response of granitic residual soil under different cyclic stress ratios and different fiber contents.

Abstract:The long-term seepage characteristics of fluid flow in saturated soils are of great importance. The Riemann-Liouville (R-L) fractional derivative was adopted to modify classical Darcy’s law (hereinafter referred to as modified seepage model) to describe the evolution of soil permeability during the long-term seepage process. Data fitting of experimental results given in published literature shows that the modified seepage model could more accurately describe the nonlinear evolution of fluid velocity with time. Moreover, the anomalous permeability coefficient value obtained with the modified seepage model is found to be reasonable. The R-L fractional diffusion equation was derived by integrating the modified seepage model into the one-dimensional Biot consolidation model. The explicit (time domain)-implicit (space domain) difference method was employed to discretize the above equation, and the correctness of the algorithm was verified through two numerical examples. On this basis, the influence of the modified seepage model parameters on the one-dimensional consolidation process of saturated soils was investigated. The results show that the fractional order β reflects the degree of soil permeability decay. The higher the fractional order, the lower the soil permeability, which leads to a further decrease in the consolidation rate; additionally, the permeability coefficient k plays a more dominant role than kβ. Thus, k should not be assumed to be zero to simplify the fitting process.

Abstract:The strength and deformation characteristics of overconsolidated clay depend on state factors such as initial void ratio, stress path and preconsolidation pressure. To characterize the state dependence of overconsolidated clay, we define two state parameters: the density-state parameter and the stress-state parameter. The former describes the void ratio difference between the current state point and the corresponding state on the critical state line, and the latter describes that between the dyadic state point and the critical state line. A new stress-state equation is then derived. Finally, the state hardening rule is adopted to describe the hardening law of the subloading surface where the current state point lies, and a state hardening model suitable for overconsolidated clay is established. Comparisons between model predictions and triaxial compression test results of different clays under drained and undrained conditions show that the proposed model exhibits good performance. The results show that stress history affects the stress-state equation of clay. The density-state and stress-state parameters in this equation approach zero when the soil reaches the critical state, and they characterize the compactness and moisture state of the soil respectively. The proposed state hardening rule can reasonably describe the strain softening and dilatancy of overconsolidated clay under drained shear, as well as the effective stress paths and the evolution of excess pore water pressure under undrained shear. The established clay state hardening model has a simple form with a single yield surface. Its material parameters can be calibrated by conventional laboratory tests, so it has good prospects for theoretical application in engineering practice.

Abstract:To reduce the degradation of strength and prevent disintegration of carbonaceous mudstone under wet and dry cycling, tests on the unconfined compressive strength (UCS) and disintegration of silicone-modified carbonaceous mudstone under wet and dry cycling were carried out. The effects of the number of dry and wet cycles and the amount of organosilicon on the UCS, grain size gradation, inhomogeneity coefficient and curvature coefficient of the modified carbonaceous mudstone were studied, and the inhibition effect of organosilicon on the strength deterioration and disintegration characteristics of the charcoal mudstone was clarified. The changing pattern of microstructure of organosilicon-modified carbonaceous mudstone was also analyzed by scanning electron microscopy (SEM) to reveal its mechanism of inhibiting disintegration. The results showed that the pattern of modified carbonaceous mudstone was positively correlated with the organosilicon content and negatively correlated with the number of wet and dry cycles. Organosilicon can effectively increase the grain size of carbonaceous mudstone, and the content of coarse particles larger than 2 mm, the maximum grain size(D_max) and the minimum grain size (D_min) of modified carbonaceous mudstone were significantly increased after the incorporation of organosilicon. Meanwhile, the particle content of modified carbonaceous mudstone in the [10 mm, 20 mm), [5 mm, 10 mm) and [2 mm, 5 mm) grain groups changed most drastically during the disintegration process, but the greater the organosilicon content, the smaller the magnitude of the change in grain size. Moreover, the higher the organosilicon content, the smaller the change in particle size. The median grain size (d₅₀), Weibull distribution parameters (λ, k), fractal dimension (D), disintegration resistance index (I_dn) and disintegration ratio (D_r) of modified carbonaceous mudstone were positively correlated with organosilicon content and negatively correlated with the number of wet and dry cycles. However, the variation rule of the inhomogeneity coefficient (C_u) is opposite. Organosilicone mainly inhibits the strength deterioration and disintegration of carbonaceous mudstone particles by crosslinking them via a network structure and the formation of a hydrophobic film on the surface layer.

Abstract:The dangerous rock in the Three Gorges Reservoir area has the characteristics of concealment, sudden occurrence, strong destructiveness, and great hazard. The deterioration of rock mass caused by periodic fluctuations of reservoir water level has become a critical threat to the long-term stability of these hazardous rocks. In recent years, scholars have conducted extensive research on the damage and disaster mechanisms of rock mass under the influence of water level fluctuations, as well as on instability models of dangerous rocks and stability calculation methods. Comprehensive analysis and research have led to the conclusion that advancements in testing methods, techniques, and equipment for assessing rock mass damage caused by water-rock interaction have deepened the understanding of disaster mechanisms related to rock mass deterioration and instability modes of dangerous rocks influenced by water level fluctuations. Furthermore, various calculation methods for evaluating dangerous rock stability have been developed. However, there are still six areas worthy of further study: disaster mechanisms and failure characteristics related to water-related hazardous rocks; laboratory simulation experiments under complex dynamic mechanical environments, in-situ tests, and large-scale structural plane detection; regularity and spatial expression of rock mass damage; studies on instability models for dangerous rocks under complex dynamic conditions; cumulative damage assessment and long-term stability studies; instability failure modes associated with water-related hazardous rocks; as well as application of remote sensing technology and machine learning methods.

Abstract:Traditional creep models are difficult to characterize the complete creep behavior of rock. In order to reveal the unloading creep mechanical properties of granite, the high-potassium calc-alkaline I-type granite of a pumped storage power station was taken as the research object, and the triaxial unloading creep test under the constant axial pressure and unloading confining pressure stress path was carried out. The creep strain characteristics and rock damage evolution pattern of granite during the unloading process were analyzed. Based on the fractional calculus theory, a variable coefficient non-integer order unloading creep damage model which can accurately describe the whole process of granite creep was constructed and extended to the three-dimensional stress state. The results show that in the triaxial unloading creep test, with the decrease of confining pressure, the total axial creep strain of each stage of the sample increases continuously, and the total axial strain is dominated by instantaneous elastic strain. The rock exhibits strain softening characteristics and presents brittle failure. The parameter identification and fitting of the triaxial unloading creep test data were carried out by using the variable coefficient non-integer order unloading creep damage model. The fitting results show that the model can better describe the creep damage evolution characteristics of the high-potassium calc-alkaline I-type granite in the Yanshan period.

Abstract:In the construction of underground rock engineering, complex geological conditions are commonly encountered, especially special conditions such as karst caves and faults, which bring great challenges to pile foundation construction. To study the accuracy of pile foundation drilling data under complex karst geology, this paper takes the pile foundation project in Yinshawan Karst Area, Jiujiang, Jiangxi as the engineering background, and summarizes the spatial characteristics of cave gradient angles based on the drilling data of the whole site, and uses the JC method to analyze the reliability of drilling data. The results show that the cave occurrence rate of the boreholes in this karst pile foundation construction site exceeds 50%, and the karst is extremely developed. According to the four spatial distribution modes of cave gradient angle, the drilling data with higher accuracy of karst cave information are preferentially selected. The JC method is used to analyze the reliability of the data with lower accuracy, and it is found that the gradient angles calculated by taking small, medium and large cave depths as reference values all follow a normal distribution, and the accuracy of identifying cave characteristics via boreholes increases significantly with the increase of cave depth. Finally, to control the supplementary drilling rate, a data screening and optimization strategy is proposed. Through the comparison of quantitative indicators, it is verified that controlling the supplementary drilling rate at about 5% can significantly improve the reliability of drilling results.

Abstract:Pile foundation is easy to develop necking during construction and service, which would bring potential safety hazards to the superstructure. Clarifying the characteristics of horizontal bearing capacity of a necking pile with cap is important for engineering design and reinforcement repair. Transparent soil made by fused silica sand and pore liquid with the same refractive index is utilized to carry out model experiments and investigate the effect of necking on the horizontal bearing capacity of a necking pile with cap. The soil deformation around piles was obtained after processing the soil particle speckle field assisted with Mat-PIV incremental program. Subsequently, three-dimensional finite element numerical simulations are incorporated to explain the change reason of horizontal bearing capacity induced by necking. Results show that necking would weaken the transfer capacity of horizontal load along pile shaft, and drive the deformation of upper pile shaft and soil resistance on pile side to increase. The ultimate horizontal bearing capacity decreases with the increase of necking dimension or the reduction of the distance from necking to pile top. The pile bending can cause the pile cap to develop oblique downward displacement, which would exert vertical pressure on the soil. Subsequently, the strength of the shallow soil is enhanced and the developed friction limits pile deformation, resulting in the improved bearing capacity of the pile.

Abstract:It is generally inevitable that the construction of high-speed railways induces overall or local damage to railway embankments in mountainous areas owing to complex topographic and geological conditions. With the development of geotechnical reinforcement techniques, more and more mountain railway embankments adopt geosynthetic reinforcement to solve the deformation and failure of embankments. However, the dynamic response characteristics and deformation patterns of reinforced embankments under inclined stratum conditions are still ambiguous. Based on comparative model tests of reinforced railway embankments with and without inclined bedrock, this paper investigates the dynamic response characteristics of geosynthetic-reinforced railway embankments under inclined stratum conditions. A comparative analysis of the evolution patterns of the vertical displacement, acceleration, dynamic soil pressure, and geogrid strains of geosynthetic-reinforced railway embankments was conducted. The results show that the peak vertical displacement of the inclined bedrock embankment is slightly larger than that of the uninclined one, and the peak vertical displacements of both cases decrease with the increase of loading frequency. The peak vertical acceleration and peak vertical dynamic soil pressure of the inclined bedrock embankment are obviously larger than those of the uninclined one, and both increase with the increase of loading frequency and decrease with the increase of embedment depth. When the embedment depth is the same, the soil below the loading center of the embankment has the largest peak vertical acceleration and peak dynamic soil pressure, followed by the side away from the bedrock, and the side near the bedrock has the smallest values. The peak strains of the embankment geogrids all decrease with increasing embedment depth of the geogrids, and the two layers of geogrids near the top of the embankment decay less, whereas the peak strain of the geogrids of the inclined bedrock-reinforced embankment is about twice as much as that of the uninclined bedrock-reinforced embankment at the same loading frequency.

Abstract:The large number of waste tires has led to increasingly severe pollution. The engineering application of waste tires is one of the ways to dispose of them. Waste tires have good engineering properties, such as high strength and corrosion resistance. Studying their role in subgrade construction is of great significance for guiding the construction of reinforced subgrades with waste tires. However, existing research mainly focuses on the reuse of tire fragments, and there is insufficient research on the reuse of whole tires. In order to further investigate the influences of filler types and geogrid reinforcement on whole waste tire reinforced subgrades, three model tests were conducted to analyze their load-bearing deformation behavior. Subgrade top-surface displacements, vertical soil pressures, and tire strains under different stress levels were analyzed. The research results indicate that the tire reinforcement layer is conducive to the distribution of additional stress, and as the load increases, the role of the tire reinforcement layer in distributing stress gradually enhances. Laying geogrids below the tire reinforcement layer effectively increases the overall stiffness of the reinforced zone and reduces subgrade deformations. The combined effects of the tire and geogrid increase the distribution angle of additional stress in the soil near the tire reinforced zone, and geogrids share some loads, reducing tire deformations.

Abstract:The resourceful utilization of chelated fly ash in road engineering can reduce the occupation of land resources, but there is no consensus on its feasibility as subgrade filler. Through lab experiments and microscopic analysis, the physicochemical properties of chelated fly ash, as well as the influence of moisture content and dry density on its engineering characteristics, were investigated in this study. The feasibility of employing chelated fly ash as subgrade filler in highway construction was explored, accompanied by proposed construction control indicators and measures to prevent environmental pollution. The results show that chelated fly ash is classified as a type of high liquid limit silt featuring a complex microstructure and low specific gravity, with a higher optimum moisture content and lower maximum dry density compared to common fillers. The primary chemical elements in chelated fly ash are Ca, Na, Si, and Cl, with major mineral components including calcium compounds, silicon dioxide, and chlorides. Calcium compounds can solidify fly ash by chemical precipitation. Strength, effective cohesion, and effective internal friction angle decrease approximately linearly with increasing moisture content, and increase with increasing dry density, while permeability coefficient decreases with increasing dry density. Chelated fly ash is suitable for highway subgrade filler, with recommended moisture content ranging from 22.0% to 29.5% for embankments and 24.5% to 29.5% for roadbed materials. To ensure subgrade stability and reduce environmental pollution risks, it is recommended to employ low liquid limit clay cover and waterproof geotextiles core-wrapping for combined treatment.

Abstract:Membrane structures are sensitive to wind loads and generate large vibrational displacements under wind loads, while the wind-resistant design of membrane structures lacks support from reliability theory. The random vibration model and reliability theory of membrane structures under wind load can provide a reference for the wind-resistant design of membrane structures. The skeleton-supported saddle membrane structure is taken as the object. Based on Von Karman’s large deflection theory and potential flow theory, the theoretical model of random vibration under wind load is established, and the approximate theoretical formula of wind-induced dynamic response is obtained using the perturbation method combined with MATLAB software. In accordance with the first-passage failure criterion of displacement, the reliability performance function of the skeleton-supported saddle membrane structure is established, and the reliability index and failure probability are obtained by means of the first-order second-moment method. The wind tunnel test of the skeleton-supported saddle membrane structure is conducted, and the vibration law at each point of the membrane is analyzed in terms of flow velocity and pressure. The percentage difference is introduced to compare the theoretical results with the experimental results, and the sensitivity analysis of the parameters affecting the reliability is carried out. The results show that the theoretical results are in good agreement with the experimental results. The rise-span ratio, pretension and wind speed all have a certain influence on the reliability of membrane structures. However, an examination of the trend of failure probability indicates that the rise-span ratio exerts a more substantial influence on the reliability of membrane structures than other variables.

Abstract:As the risk of falling caused by deterioration of exterior wall tiles has become increasingly prominent, a multiple linear regression model is proposed to rapidly assess the deterioration degree based on field surveys. This method aims to reduce the ambiguity of existing assessment approaches while improving diagnostic efficiency. Firstly, the types of deterioration and their impacts on exterior wall tiles were classified and analyzed according to the available research, and qualitative assessment standards for deterioration were summarized. Then, the image library covering the deterioration of exterior wall tiles was established through surveys, and grouped evaluation of the deterioration based on the proposed standards was conducted. Subsequently, an assessment model for the deterioration was built using a multiple linear regression approach, with a determination coefficient R² of 82.45%, and the impact of independent variables on dependent variables was statistically significant. To further standardize the assessment results, a value function was introduced to process the model output, obtaining normalized deterioration degree assessment values. Finally, combining the regression model, value function, and rating standards of deterioration degree, a complete set of assessment approaches was formed. Compared with traditional assessment methods, this approach has the advantages of being comprehensive, simple, efficient, and highly applicable.

Abstract:In order to reasonably evaluate the post-earthquake traffic function of railway bridges, a methodology founded upon a fault tree model was proposed for the purpose of assessing the functional state of railway simply supported bridges. First, an investigation was conducted into the correlation between damage to bridge components and post-earthquake functionality of the structures. To this end, a fault tree model was developed, with the post-earthquake functionality of the bridge designated as the top event. Thereafter, seven seismic failure modes were defined according to the basic events of the fault tree. A post-earthquake functional state assessment process for bridges was established considering different seismic failure modes. Finally, taking typical railway simply supported bridges with a span length of 32 m in Southwest China as a reference, this study used OpenSees to establish 1 000 full-bridge finite element models with different structural parameters. The proposed method was applied to assess the seismic failure modes and post-earthquake functional states. The findings indicate that the primary seismic failure modes of bridges involve combined damage to bearings and other components. With the increase in earthquake level, the post-earthquake traffic function of railway bridges decreases significantly. The failure mode involving combined damage to the rails and other components is the key factor contributing to the decline in the post-earthquake traffic function of railway bridges.

Abstract:Bridge inspection and service performance evaluation are critical technologies for ensuring the safe operation of bridges. Utilising a multi-scale perspective, the paper systematically reviews the academic progress and future trends in the field of bridge damage detection and assessment. The research is explored from three different scales: macro, meso, and sub-micro. A thorough analysis of the evolution of bridge feature detection methods is presented at the macro level, illuminating the trend of transformation toward rapid detection technologies based on vehicle responses. At the meso- and sub-micro scales, the complexity of bridge surface damage has resulted in research focusing on recognition methods based on computer vision. In terms of service performance evaluation, the extant methods for short-term bridge condition assessment and long-term condition prediction are summarized. The comprehensive analysis shows that the current bridge inspection technology has been effective in identifying bridge damage features. However, future research should still focus on two directions: macro damage identification based on vehicle response and meso- and sub-micro damage identification based on computer vision. Both directions have shown great application potential. Future research should further optimize vehicle-bridge coupled response models and improve their applicability to different forms of macro-scale damage; Study the mapping relationships between meso- and sub-micro-scale damage images and bridge mechanical characteristics; conduct research on multi-scale damage correlation to improve detection accuracy; and explore more practical evaluation methods for bridge service performance based on engineering practice.

Abstract:Sliding bearings represent a prevalent type of bearing in cable-stayed bridges, and are also one of the important force-transmitting components of bridges. Sliding bearings are often worn during operation, resulting in the load transfer function and the displacement and rotation deformation function being affected, and there are certain hidden dangers to the safe operation of bridges. Therefore, it is of great significance to analyze the influence of sliding bearing performance changes on the overall mechanical properties of cable-stayed bridges. Based on the finite element model of cable-stayed bridges considering bearing wear, this paper analyzes the influence of sliding bearings on the static and dynamic performance of cable-stayed bridges in different degrees of wear. Taking a cable-stayed bridge as an example, a spatial three-dimensional finite element model of a cable-stayed bridge considering sliding bearing wear and other boundary conditions is established. The displacement-friction relationship of sliding bearings during progressive wear is simulated. The modal performance, static performance and dynamic response of the cable-stayed bridge are comparatively analyzed when the sliding bearings are worn to different degrees, and the degradation law of the overall mechanical properties of the cable-stayed bridge is obtained when the sliding bearing is damaged. The findings of the study demonstrate that the occurrence of sliding bearing wear leads to an augmentation in bridge stiffness. This, in turn, results in an escalation in the frequencies of the cable-stayed bridge, especially for longitudinal drift and vertical bending modes, increases the girder end axial force significantly and reduces the cumulative bearing displacement. The bearing cannot adapt to the deformation needs of the girder, resulting in a buildup of internal forces in the girder and bearings.

Abstract:As the service life increases, the bridge performance deteriorates continuously, and the damage to structural components intensifies and spreads to adjacent components. The process of multiple independent updates of finite element models based on random search algorithms fails to reflect the dynamic variation of bridge service performance. The present paper puts forward a dynamic calibration method for bridge finite element models considering structural performance degradation based on the Cuckoo Search Algorithm (CS algorithm). Firstly, the set of parameters to be updated, which corresponds to the code of the CS algorithm, is divided into three groups: diseased components, adjacent components to diseased components, and other components. Subsequently, a range of strategies are employed to initiate each group. The upper limit of the parameters to be updated is set to the previous update result. In conclusion, the search range for each group of codes is limited by setting different control factors for step sizes. At the end of the paper, a single-span truss bridge was used to verify the effectiveness of the proposed method. The research results indicate that the dynamic calibration method for finite element models based on the CS algorithm can dynamically calibrate the finite element model of bridges. The dynamically calibrated finite element model can describe the time-varying behavior of the service performance of bridges as the damage deepens and spreads to adjacent components.

Abstract:The geosynthetic reinforced soil integral bridge, as a novel type of abutment, demonstrates significant application value in small-span bridges and culvert engineering. At present, the research on its operational mechanisms is limited, particularly with regard to the bearing capacity characteristics of abutments, which have seldom been studied. Taking the ?erovinci Bridge in northern Slovenia as the prototype and based on abutment static load test technology, this paper carries out static load tests on an integral-wall geosynthetic reinforced soil abutment model. The analysis encompasses the settlement at the top of the abutment, the displacement of the facing panel, the horizontal displacement of the soil behind the facing panel, the distribution of reinforcement strain, and the pattern of the potential failure surface. The measured tensile force of the abutment reinforcement is compared with the calculated values recommended by three codes. The results indicate that under the action of large load, the junction of the front wall and the two wing walls is the weak link of the structure; under the maximum load, the top settlement of the abutment does not exceed the serviceability limit and strength limit recommended by the code. The horizontal displacement of the middle panel of the abutment is the largest, and the wall surface is bulging in the middle as a whole; the maximum soil displacement behind the front and wing wall panels occurs at the top of the model; the maximum strain of the reinforcement is always between 0.5 m and 0.65 m, and the reinforcement strain decreases linearly with the increase of distance away from the panel. Under specific loading conditions, the maximum strain of longitudinal reinforcement remains below the specified limit; the potential failure surface of the abutment develops, with the lower part close to the Rankine failure surface, and the upper part being the failure surface of the back edge of the non-bearing area; the calculated stiffness values agree well with the measured maximum tensile force of the reinforcement.

Abstract:During the operation of a subway, vibrations generated on steel rails propagate in the form of stress waves along the path: rail-rail pad-sleeper-ballast-tunnel-soil. In order to investigate variations in the fundamental characteristics of stress waves along this propagation path, we constructed an indoor model of a subway tunnel with steel rails. A Laser Doppler Vibrometer (LDV) was used to measure stress wave signals at different locations of the experimental model, and a scanning LDV was employed to capture the real propagation process of stress waves on different surfaces of the steel rails. Finally, the finite element simulation software LS-DYNA was utilized to perform a comparative analysis of the changes in wave field characteristics during stress wave propagation from an image perspective. The research results indicate that the stress wave signals generated by the wheel-rail interaction on the steel rails are mainly characterized by low-frequency signals ranging from 25 to 400 Hz and high-frequency signals at 1 400 Hz. Conversely, the stress wave signals propagating into the soil primarily consist of low-frequency signals ranging from 25 to 200 Hz. A comparison between the measured data and test results of the experimental model demonstrates that the steel rail model exhibits dynamic performance consistent with the actual subway tunnel. The analysis of signal data and wave field contour maps both indicate that the high-frequency components of stress waves attenuate most rapidly during propagation from the steel rail to the concrete sleeper, exhibiting the lowest signal energy transfer rate. The comparison of stress wave fields from LDV measurement and computer simulation intuitively validates the accuracy of the simulation method from an image perspective. Additionally, this study suggests that LDV measurement results can serve as an alternative to computer simulation results for investigating wave fields in complex media and models.

Abstract:The strength of high-performance concrete has an intricate relationship with its components. It is evident that traditional black-box models are characterised by an absence of interpretability. As a result, they fail to reveal the actual dependency between concrete strength and its components. Using a large sample dataset of high-performance concrete, machine learning models are constructed and optimized with the Hyperopt algorithm. The models are integrated with SHAP explainability techniques and feature dependency algorithms. A visual representation of the nonlinear relationship between the strength of high-performance concrete and its components is calculated. Furthermore, the interaction and coupling effects between multiple components are examined. The results indicate the following: Hyperopt-extreme gradient boosting model is a trusted machine learning model with high accuracy and robustness. Among the eight components(factors), age, cement, water and slag play a key controlling role in compressive strength, and their relationships with compressive strength satisfy the exponential function, power function, Gaussian function, and exponential function, respectively. At the same time, there is a significant interactive coupling effect between the four key factors; the interaction curves between age and cement, water, and slag adhere to the LogisticCum, LogNormal2D, and Power2D functions. The interaction between cement and water, as well as between cement and slag, conforms to the Poly2D function, while the interaction between slag and water conforms to the ExtremeCum function.

Abstract:Bimetallic electrocatalysts have been shown to exhibit synergistic effects, facilitating the efficient catalysis of neonicotinoid pesticides degradation. However, their application is constrained by diminished active sites arising from the aggregation of metal nanoparticles. By anchoring metallic species onto nanofibres through electrospinning and achieving the in-situ integration of metal oxides with carbon fibres via thermal treatment, we successfully constructed a carbon fiber-anchored ferromanganese bimetallic electrocatalyst (FM@N-CNF), featuring uniformly dispersed metal oxides with an average particle size of 6 nm. Electrochemical characterisation confirmed that FM@N-CNF exhibited a superior electrochemically active surface area and electron transfer capability compared with monometallic catalysts. When employed as a cathode material at -0.5 V vs. SCE, FM@N-CNF achieved complete degradation of thiamethoxam within 90 minutes and maintained degradation rates above 80% over 10 consecutive cycles. The catalyst demonstrated favorable tolerance under the conditions of pollutant concentrations ranging from 5~100 mg/L, pH values of 3~11, and the coexistence of common inorganic salts. Quenching experiments in combination with electron paramagnetic resonance (EPR) spectroscopy consistently identified singlet oxygen (¹O₂) as the predominant reactive oxygen species. Liquid chromatography-mass spectrometry analysis revealed that the degradation pathway of thiamethoxam primarily involves carboxylation and carbonylation reactions.

Abstract:Landfill leachate is a complex organic wastewater produced by sanitary landfills, which contains high concentrations of pollutants and is difficult to treat. Anodic oxidation represents a sophisticated technological advancement within the domain of electrochemical oxidation, characterized by high efficiency and low environmental pollution. However, its application is limited by available electrode materials. The Ti₄O₇ electrode is the key to solving the problems of electrode materials for anodic oxidation because of its strong conductivity, corrosion resistance, high oxygen evolution potential and low cost. At present, Ti₄O₇ electrodes have been used to degrade a variety of organic pollutants, including landfill leachate treatment, showing broad application prospects. In this study, a Ti₄O₇ anode reactor was constructed, and two configurations includind were used to Flow-by and Flow-through treat the landfill leachate biochemical effluent. The optimal treatment conditions were determined by considering time, current density, pH, chloride ion concentration and other factors. The experimental results show that the Flow-by mode removes COD up to 77.47% under the optimal conditions, which is better than the 60.56% of the Flow-through mode. Flow-by mode can also change the DOM composition more effectively, with higher initial treatment efficiency, and can mineralized and remove most dissolved organic matter. In treating, the Ti₄O₇ anode reactor has significant advantages in treating landfill leachate.

Abstract:Heavy metal contamination stemming from industrial waste is an increasingly grave issue with extensive repercussions for human health and ecological environment. Biochar has been demonstrated to have significant potential in the remediation of heavy metal pollution. However, the effectiveness of raw biochar is constrained under conditions of low pH and high heavy metal concentrations. In order to address this challenge effectively, this study utilized dragon fruit peels as precursors to prepare biochar via pyrolysis at 500 °C for 2 hours. The development of an efficient green adsorbent termed GBMSs (green biochar-metakaolin-sodium silicate) has been accomplished. Response surface methodology (RSM) tests revealed that GBMSs exhibited exceptional adsorption performance for zinc, achieving up to 67.37 mg/L at pH=2. Kinetic and isothermal adsorption studies indicated that adsorption of Cu and Zn onto GBMSs closely followed the Langmuir model and the pseudo-second-order kinetic equation, suggesting homogeneous monolayer surface adsorption with a rapid adsorption rate, and the adsorption capacity increased with rising pH. In-depth analysis using XRD and SEM-EDS techniques identified chemisorption as the primary adsorption mechanism, with ion exchange, surface complexation, and co-precipitation playing significant roles. These findings confirm that GBMSs, as an environmentally friendly and efficient adsorbent, holds considerable promise for the treatment of heavy metal pollution.

Abstract: