Abstract:To examine the impacts of freeze-thaw cycles on the performance of geogrid reinforced soil slope and the inhibition effect of reinforcement on sand slope deformation， two model tests were conducted on 1.2 m high slopes subjected to 7 freeze-thaw cycles under -25 ℃ and 30 ℃ conditions. The tests compared the performance of reinforced and unreinforced slopes， analyzing qualitative and quantitative variations in heat transfer， moisture migration， settlement， and lateral deformation of the slopes under freeze-thaw cycles. The results indicated that the slope temperature exhibited periodic changes during freeze-thaw cycles， with diminishing influence of external temperature from the free surface inward. During freezing， moisture migration within the slope occurred bidirectionally toward the free surface and base， while vertical migration predominated during thawing due to gravity. The slope settlement demonstrated periodic frost heave and thaw subsidence， with cumulative total settlement increasing with the number of freeze-thaw cycles. The slope displacement displayed freeze-expansion and thaw-induced contraction， and the total displacement increased with the number of freeze-thaw cycles. Reinforcement hindered vertical moisture migration within the slope， thereby changing the temperature field of the slope， and reinforcement effectively mitigated the deformation of the slope caused by freeze-thaw action.

Abstract:During the construction of double-layer porous asphalt pavement， a binder layer needs to be laid to ensure that the upper and lower layers are bonded by enough binding force to resist potential pavement diseases during service. To investigate the dosage range and force characteristics of the binder layer of double-layer porous asphalt pavement， this paper utilized the pressure film and pavement texture scanner to obtain the interlayer contact characteristics of both single-layer and double-layer porous asphalt pavement， thereby determining the recommended dosage of the binder layer for the double-layer pavement； and the oblique shear test was conducted to obtain the failure characteristics of the binder layers in both single-layer and double-layer porous asphalt pavement. The results indicate that the interlayer contact area of the double-layer porous asphalt pavement is larger， which is approximately 1.5 times that of the single-layer porous asphalt pavement. The OGFC mix used in the lower layer of the double-layer porous asphalt pavement exhibits more microscopic concave and convex structures and a larger surface area， which is about 1.18~1.20 times that of the AC mix. Based on the surface area multiplier relationship and the standard recommended value， it is recommended that the dosage of the binder layer for double-layer porous asphalt pavement be 0.8~1.2 L/m2. The shear resistance of the binder layer in double-layer porous asphalt pavement is superior to that in single-layer porous asphalt pavement. The interlayer shear strength of single-layer porous asphalt pavement is solely provided by the bonding force of the binder layer. The interlayer shear strength of double-layer porous asphalt pavement is provided by the bonding force of the binder layer and the interlocking of interlayer particles. After reaching the maximum shear force， the interlayer particles continue to resist shear deformation， and the shear resistance does not decline abruptly.

Abstract:Recoverable anchors， characterized by low carbon footprint and environmental friendliness， have been increasingly applied in urban foundation pit support projects. However， the evolution of their bearing performance under cyclic traffic loading has not been thoroughly studied. In this study， element-scale tests were conducted to examine the mechanical characteristics of the anchor-rock interface under different cyclic loading parameters. These tests captured the complete shear stress-shear displacement curve （i.e.， τ-s curve） of the anchor-rock interface under cyclic loading. Based on the experimental results， a unified model was developed to describe the degradation of shear strength at the anchor-rock interface， accounting for the effects of the reference load ratio and the number of load cycles. Based on the morphological characteristics of the τ-s curve at the anchor-rock interface， a composite τ-s curve model for the anchor-rock interface was established， consisting of a linear segment and a sudden drop curve. Furthermore， a unified degradation model for the τ-s curve of the anchor-rock interface was developed， accounting for the effects of the reference load ratio and the number of load cycles. The model demonstrates good predictive performance. Finally， a theoretical framework of load transfer of recoverable anchors under cyclic loading considering the Poisson effect was established， and the influence of cyclic loading on the ultimate bearing capacity of engineering anchors was investigated. The research results can provide a reliable theoretical basis for the engineering application of recyclable anchors.

Abstract:Modular steel structures as an efficient， environmentally friendly， and sustainable construction method， and the connection between the units will directly affect the overall stability and seismic performance of the structure. However， the common connection methods in modular steel structures， such as welding， bolted connections， and prestressed connections， exhibit several challenges including low construction efficiency， susceptibility to installation errors， and limited working space. In this paper， a novel shear key double-layer grouting connection is proposed， which has good applicability to corner column joints， side column joints and middle column joints of modular steel structures. In order to evaluate the axial mechanical properties of the novel connection， 8 connection specimens were produced for push-out tests， and the effects of shear key spacing， grout strength， connection length and number of grout layers on the failure forms， tensile capacity and strain distribution of the specimens were investigated. Based on the theoretical analysis， the formula for calculating the tensile capacity of the shear key double-layer grouting connection is derived. The effectiveness and accuracy of the formula are verified by comparing with the test results， which can provide a theoretical basis for the engineering application of the novel connection in the modular steel structure.

Abstract:The rapid urbanization has led to a tightening of land resources， often resulting in structures with small spacing between adjacent buildings. Under dynamic loads such as earthquakes， this may cause excessive relative displacement between adjacent structures， potentially leading to collision-induced damage. This paper proposes an energy-dissipation enhanced torsional eddy current damper （EDE-TECD） for vibration reduction in adjacent structures. The basic structure and operational mechanism of the EDE-TECD are first explained. Based on a rack-and-pinion speed amplifying device， a damping coefficient estimation formula for the EDE-TECD is derived. A simplified motion equation for two adjacent structures with EDE-TECD applied is established， and using the optimization criterion of maximizing the minimum damping ratio between adjacent structures， a numerical search method is employed to obtain the optimal inertial mass ratio and damping ratio for the two-degree-of-freedom adjacent structure system with EDE-TECD. An analysis of the optimal inertial mass ratio is conducted， leading to a design process for the optimal parameters in the practical application of EDE-TECD. Additionally， the vibration reduction performance of adjacent structures with either EDE-TECD or linear viscous dampers is compared. Finally， the influence of structural stiffness degradation on the vibration reduction performance of EDE-TECD is studied. The results show that the optimal inertial mass ratio obtained through numerical search may be negative. Increasing inertial mass ratio does not always improve the damping ratio of the structure’s lower modes. Under 10 sets of earthquake wave tests， the optimized EDE-TECD significantly reduces the relative displacement of adjacent structures under seismic action， with the peak vibration reduction rate averaging 64.79%， which is 8.42% higher than that of linear viscous dampers. And under the El Alamo earthquake wave， when the structure’s stiffness is reduced by 10% to 40%， the maximum decrease in the peak damping rate of EDE-TECD is only 6.29%， and the structure can still maintain good damping performance.

Abstract:A series of explosive thermal spalling tests at elevated temperature and compression tests after high temperature were conducted on coir fiber reinforced ultra-high performance concrete （UHPC） by using an electric furnace in this study， aiming to shed light on the influence of the length and volume dosage of coir fiber on the fire resistance of UHPC exposed to different high temperatures. The results indicate that incorporating 1% of coir fibers with a length of 2 cm in UHPC can effectively suppress the high-temperature spalling. Microscope analysis reveals that a tangential pore network is generated between coir fibers and UHPC matrix due to shrinkage， decomposition， and carbonization of coir fibers at high temperature， which provides channels for the escape of internal water vapor as well as improving the thermal spalling resistance of UHPC. At 200 ℃， 400°C， 600 ℃， and 800 ℃， compressive strength and elastic modulus of UHPC， incorporating 1% of coir fibers with 2 cm long， significantly decrease with an increase in control temperature. Also， within the range of the control temperature， the ratio of the axial compressive strength to the cubic compressive strength varies between 0.62 and 0.92. On the other hand， compressive strength and elastic modulus decrease with the increasing volume dosage of coir fiber under the same control temperature， and the ratio of uniaxial compressive strength and cubic compressive strength varies with control temperatures. In terms of the improvement effect on fire resistance of UHPC， coir fiber is superior to steel fiber and is comparable to jute and flax fibers. Based on the test data and the existing formula， a special formula is proposed for evaluating the residual compressive strength of coir fiber reinforced UHPC exposed to high temperatures.

Abstract:To facilitate engineering applications and quantitatively describe the damage level of concrete components， referring to the constitutive model of concrete mentioned in Appendix C of the current Chinese standard “Code for Design of Concrete Structures” GB/T 50010—2010， this paper proposes a damage assessment method for concrete components based on material damage. That is， the damage level of the component is defined according to the values of the damage evolution parameter. It is specified that when the damage evolution parameter dc（t） is less than the damage evolution parameter dc（t），r corresponding to the peak strain of concrete εc（t），r， the concrete component is in a non-damaged state （Level L1）； when the damage evolution parameter dc（t） is greater than the damage evolution parameter dc（t）u corresponding to the strain of concrete εc（t）u， the concrete component is in a severely damaged state （Level L6）； when the damage evolution parameter dc（t） is between the two values， the damage state of the concrete component （Levels L2 to L5） is evaluated by the linear interpolation method. To verify the rationality of this method， a refined model of 18 beams and 2 columns was established using the ABAQUS software， and numerical analysis were conducted. The simulation results show a good agreement with the test results. According to the damage assessment method proposed in this paper， most of the beam components under the peak load and the column components under the yield load are in a severely damaged state （Level L6）. However， when using the damage assessment method based on the compressive strain of concrete as mentioned in the “Standard for Performance-Based Seismic Design of Building Structures” T/CECA 20024—2022， most of the components are in a moderately damaged state （Level L4）， while a minor portion of the components are in a relatively severe damaged state （Level L5）. From a macroscopic perspective， the damage assessment method for concrete components based on material damage proposed in this paper is more consistent with the actual expectations for evaluating the damage of concrete components and has a certain reference value.

Abstract:The structural performance of modular buildings depends largely on the overall performance of their joint connections. This paper takes bolt-connected vertical joints of fully assembled modular construction-reinforced concrete （FAMC-RC） as research objectives， and a series of out-of-plane uniaxial tensile tests are conducted out on 10 groups of full-scale specimens of individual bolted vertical joints. The results show that under the action of tensile loading， the vertical joint may exhibit failure modes such as eccentric bending failure of a beam， punching shear failure of the plate， combined flexural and punching shear failure of the plate， and shearing failure of the plate. The damage process mainly undergoes four stages of prestressing loss， elastic loading， elastic-plastic development， and brittle damage. The mechanical properties of the joints are influenced by the distance D1 to the ribs， the length L of the connecting wall， and the embedded steel plate. The presence of ribs contributes to improving the out-of-plane bearing capacity of the joints， and the enhancement effect of the rib decreases with the increase of D1. The length L of the connecting wall is sufficient to make the punching cone fully carried out， and the punching ring is complete. The embedded steel plate in the joint region can obviously increase the bearing capacity， deformation capacity， and stiffness of the test specimen， but the increase in the size of the embedded part does not have a significant effect on the mechanical properties of the test specimen. Based on the above test results， the project suggests that： the distance D1 from the joint to the rib should be less than 485 mm， the length L of the connecting wall should be more than D1+300 mm， and， to reduce the amount of material， the V1-shaped embedded part is preferred. In this paper， for the punching damage mode， considering the concrete plate， reinforcement， and embedded steel plate of the three common anti-punching roles， a bearing capacity formula is proposed for the joint punching damage. The comparison with the test value concludes that the calculation formula is conservative. Taking into account the greater variability of the concrete material， the formula of the security reserve is high， and the calculation method is basically reasonable.

Abstract:To solve the problem of brittle failure at the rigid connection of the traditional h-shaped anti-slide pile beam， a structural optimization scheme was proposed， which simplified the multi-time super-static structure into an inclined “simply supported” structure and proposed the h-shaped inclined beam bearing anti-slide pile. Based on the Winkler elastic foundation beam theory and the structural force degree shift method， the analytical model was established by using the numerical analysis and numerical simulation methods. The results show that the theoretical calculation of the analytical solution is in good agreement with numerical simulation results， which proves the rationality of the calculation model. Compared with the traditional h-shaped pile， the optimized structure has significant advantages， that is， the bending moment at the connection between the rear pile and the beam is greatly reduced， the bending moment at the top of the pile of the front pile is completely released （the reduction is 0）， the shear force of the beam is significantly reduced， and the stress concentration phenomenon at the connection is avoided. From the analysis of key geometric parameters， it can be seen that with the increase of the angle of the oblique beam， the internal force and deformation of the oblique beam and the rear pile decrease， and with the increase of the distance between the front and rear piles， the internal force and deformation of the front pile decrease， and the mechanical performance of the system is better.

Abstract:Due to the influence of terrain and climate， the risk of highway slope disasters in Meizhou City is prominent. This study focuses on a 500-meter range on either side of the existing mainline highways in Meizhou， selecting eight evaluation factors—elevation， slope， curvature， lithology， NDVI， TWI， annual average rainfall， and maximum monthly rainfall—to construct a highway slope disaster susceptibility index evaluation system. Based on historical highway slope disaster data， a Bayesian network model is established to predict the susceptibility of highway slopes to disasters and further to analyze the distribution characteristics of landslide hazards under different rainfall scenarios. The conclusions are as follows： 1） The Bayesian network model for highway slope disaster susceptibility evaluation achieves an AUC of 0.832， indicating good reliability. Additionally， the SHAP values from the Bayesian network model show that lithology， slope， and maximum monthly rainfall are the three most influential factors affecting highway slope disasters in Meizhou City. 2） Considering three rainfall scenarios （1-in-10， 1-in-50， and 1-in-100-year events）， the areas of extremely high-risk regions gradually increased， accounting for 13%， 19%， and 22%， respectively. 3） Based on web scraping tools to retrieve social media data， all historical highway slope disaster cases in Meizhou are located in regions classified as high and extremely high hazard levels. The findings of this study provide a valuable reference for the prevention and control of highway slope disasters in Meizhou City.

Abstract:To analyze the precision of the integrated 3D point cloud reverse modeling （IPCRM） method in generating three-dimensional models of thin-thickness steel members， locally deformed angle steels are taken as the research objects. Three-dimensional point cloud models of locally deformed angle steels are established using the SfM （structure from motion）-MVS （multi-view stereo） algorithm， and the surface models of locally deformed angle steels are generated with the help of reverse engineering technology. Special attention is placed on model precision verification experiments. The results show that： the relative errors of all surface shape characteristic parameters are within 8% confirming the conformity of the models； there is no significant difference between the four angle steel models and the actual angle steels （P value， P=0.99）， and angle steel thickness has no significant influence on model precision （P value， P=0.95）. These conclusions hold at a 95% confidence level （significance verification）. The research results provide a basis for subsequent algorithm optimization and the rational use of this method for local deformation damage detection and bearing performance evaluation of steel members.

Abstract:To achieve precise positioning of steel bars inside concrete structures and accurate detection of early corrosion status， this article introduces a terahertz reflectance spectroscopy technique and systematically explores its potential application in non-destructive testing for structural corrosion assessment. The research results indicate that this technology can achieve precise positioning of steel bars inside the structure and accurate measurement of the thickness of the protective layer， with a positioning accuracy within 1.2 mm of the steel bars. Meanwhile， the minimum measurable thickness of the corrosion layer reaches 45 μm， which is sufficient for effective detection of early corrosion of steel bars. Terahertz technology can achieve quantitative visualization imaging of the thickness of the protective layer and corrosion layer within the scanning area， eliminating the influence of uneven distribution of protective layer thickness and providing an innovative and efficient method for early corrosion characterization of reinforced concrete structures.

Abstract:The strong permeability， high porosity， and easy disintegration of granite residual soil cause serious erosion in the surface layer of the slope. Both biocementation and plant roots can be used for shallow slope protection. This study conducted single biocementing， single root， and joint combined reinforcement tests to investigate the effects of root content and the biocementing time on permeability， water retention， disintegration， and shear properties. Then， the hydraulic properties of granite residual soil reinforced by biocementation joint root systems were systematically analyzed. The results showed that single root reinforcement primarily improved the shear characteristics of granite residual soil， but also increased its permeability. Single biocementation significantly improved the permeability， water retention， disintegration， and shear properties of granite residual soil； however， too many cementing times may weaken its shear resistance properties. The incorporation of roots under co-reinforcement increased the permeability of granite residual soil， while substantially improving the disintegration and shear properties， which was more pronounced with higher root incorporation. The disintegration process of the specimens under joint reinforcement was mainly divided into three stages， and the improvement effect of cohesion was much higher than the internal friction angle. The combined reinforcement of biocementation and root exhibits a significant synergistic effect， with biocementation playing a critical role in enhancing the hydraulic properties of granite residual soil， while root systems assist in regulating water movement.

Abstract:To accurately obtain the influence of slope transition sections on the wind field characteristics of the terrain model， this study used the large eddy simulation （LES） method to conduct numerical simulation of wind field characteristics in the transition section of slopes with different slope ratios. At the entrance of the computational domain， numerical turbulent flow was generated by the narrow band synthesis random flow generation （NSRFG） method . The slope ratio ξ（=L/h） of the slope transition section was defined （ξ takes the values of 0， 1， 2 and 3， where h is the slope height and L is the slope length）. The results show that when the incoming flow reaches the slope transition section， a backflow is formed at the bottom of the transition section， the wind speed is significantly reduced， and the turbulence intensity is also reduced. When the incoming flow reaches the top of the slope transition section， the wind speed increases significantly， and the turbulence intensity also increases. When the incoming flow passes through the slope transition section， the mean wind speed profile gradually returns to the same as that of the inlet. In addition， the larger ξ can result in better transition effect， lower vortex shedding frequency， more uniform vortex shedding frequency at different heights， smaller variation in wind speed amplification factor， and larger turbulence integral scale. The transition effect is best when ξ=3， and it returns to the same as the inlet wind speed profile at x/h=2， and the wind speed amplification factor returns to 1 at the more advanced position. This study can provide a reference for the design of boundary transition sections of terrain models for wind field characteristic measurement.

Abstract:To investigate the wind load characteristics of rectangular sections with a small side ratio （D/B<1.0）， a series of three-dimensional models （with fixed cross-sectional area and side ratios ranging from 0.25 to 1.00） were adopted. First， the space-averaged large eddy simulation （LES） method was used to obtain the aerodynamic coefficients of four models with distinct side ratios， as well as the correlation coefficients of horizontal fluctuating wind pressure across different facades of the models. Subsequently， the influence of the side ratio on the product time-history peaks and phases of wind pressure at the side-surface measurement points was compared and analyzed. Finally， based on the dynamic mode decomposition （DMD） method， a reduced-order model capable of extracting dominant modes and reconstructing the wind pressure field was established， and the wind pressure fields of models with different side ratios were analyzed. The results indicate that a decrease in the side ratio affects the separation and reattachment of flow on the model’s side surfaces， altering the wind load action mechanism and significantly reducing the horizontal correlation of fluctuating wind pressure （with the 0.25 side ratio model exhibiting the most pronounced effect）. The transition point of wind pressure fluctuation characteristics is located approximately 0.6B from the side-surface reattachment region； the wind pressure time histories at the upstream and downstream of this transition point show opposite phases and negative correlation. The first four modes extracted via the DMD method can accurately reconstruct the flow field， thereby clarifying the random wind pressure field of small side ratio models. This study provides a reference for relevant flow control and structural design.

Abstract:Taking phosphogypsum from a tailings reservoir in Guizhou as the research object， a comparison with planting soil standards revealed problems such as strong acidity， severe salinization， and poor fertility. Improvement experiments were conducted using quicklime， straw biochar， earthworm manure， and nutrient soil to obtain the optimal improvement scheme. Based on the improved phosphogypsum， studies on phytoremediation and microbial remediation were carried out to screen plants with strong stress resistance and the best fluoride pollution enrichment capacity， as well as to cultivate microorganisms with the best phosphorus pollution fixation and transformation effects. According to the experimental results， plant-microbial combined remediation experiments were conducted to compare the enrichment capacity of plants and microorganisms for pollutants， the adaptability of plant growth capacity， and the improvement effect on the physicochemical properties of phosphogypsum，so as to clarify the synergistic effect between plants and microorganisms. Finally， a plant-microbial combined remediation scheme for in-situ control of phosphogypsum pollution and ecological remediation is proposed. The results showed that when quicklime， straw biochar， vermicompost， and nutrient soil are added at concentrations of 1.0%， 1.0%， 10.0%， and 10.0%， respectively， the pH of phosphogypsum increases from 2.16 to 4.75， organic matter content increases by 5.3 times， and electrical conductivity decreases to 56.4%. Phytoremediation experimental studies found that ryegrass had the optimal stress resistance and pollutant enrichment effect； microbial remediation experiments revealed that the five strains isolated and screened from phosphogypsum all have the ability to fix and convert phosphorus. After identification， they were identified as the chitinophaga sp.， Pseudomonas sp.， Xanthomonas sp.， Variovorax paradoxus sp.， and Delftia sp.. The optimal inoculation amount was 5×107 CFU/300 g， which could reduce the phosphorus concentration of phosphogypsum leachate to 23.3%. Plant-microbial combined remediation experiments found that the addition of microorganisms had a growth-promoting effect on plants. The total phosphorus and maximum fluoride adsorption increased by 39.9% and 78.1% respectively； furthermore， the phosphorus-fixation ability of microorganisms increased by 123.2%.

Abstract:Sudden metro service interruptions can result in train delays and passenger congestion at stations. This， in turn， will present significant challenges for passenger evacuation and emergency management. To evaluate the performance of urban public transport networks under such disruptions， this paper proposes a composite network resilience assessment method based on resilience theory， which considers passengers’ multi-path decision-making for travel in the event of sudden disruptions. Firstly， the construction of an urban public transport composite network model， which considers the “one-to-many” coupling mode of stations， is based on the combination of passenger flow and geographic information data. This model is used to determine the network interruption intervals under different faulty stations. Secondly， the inter-layer traffic distribution of the network is carried out， taking into account the passengers’ multi-path decision-making in emergencies and calculating their travel times. Ultimately， an evaluation framework for the resilience of the composite network is established based on the composite network performance function. Furthermore， the network resilience levels under disparate interruption scenarios are contrasted through case analysis. The findings indicate that there are notable discrepancies in the network resilience levels under varying station failures. Among these discrepancies， the interruption interval of the network， the passenger flow volume of the lines， and the conditions of the subway-coupled bus stations will all influence the network resilience under interruptions. The resilience assessment method for urban bus composite networks proposed in this study can serve as a reference for the development of emergency response plans in the event of sudden disruptions.

Abstract:While smart card data （SCD） collected from automatic fare collection （AFC） systems accurately records when and where people travel， they do not directly convey the trip purposes or activity types. In this study， we propose a method that integrates station clustering with an LDA model to uncover latent activities from urban rail transit passenger mobility data. First， we classified the stations into eight categories—employment，residential， mixed-use residential-employment， commercial centers， tourist attractions， composite hubs， external hubs， and ridership cultivation stations—using a constrained-seed K-means algorithm， based on demographic characteristics， ridership patterns， and the distribution of POIs around each station. Second， an LDA model is developed based on four key attributes： exit time， activity duration， origin station type， and destination station type. The model successfully identifies five primary activity types： shopping-related， work-related， home-related， tourism， and other. Furthermore， these patterns are divided into several subtopics， each distinguished by specific temporal and spatial characteristics， providing the theory support for deeply figuring out holiday travel patterns of urban rail transit passengers.