30 October 2024, Volume 37 Issue 10
    

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    Pavement Engineering
  • Preparation Regulation and Functional Evaluation of Road Maintenance Energy-absorbing Seal Considering Texture Reconstruction
    WANG Chao-hui, CHEN Qian, LI Yan-wei, ZUO Zhi-wu, FENG Lei, HUANG Shuai
    China Journal of Highway and Transport. 2024, 37(10): 1-13. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The purpose of this study was to develop a new application of energy-absorbing materials in the road maintenance field and to produce a preventive maintenance seal that can improve the road surface function and enhance the structural bearing capacity of existing roads. A new road energy-absorbing material was used as the matrix, and a “sandwich” structure was used as the framework. A road maintenance energy-absorbing seal was designed and prepared, considering texture reconstruction. Image-processing analysis and accelerated loading tests were performed to analyze the decay law of the surface texture characteristics and road surface function of the road maintenance energy-absorbing seal and evaluate the durability of the seal. The effect of the road maintenance energy-absorption seal on decreasing the strain at the bottom of an asphalt concrete plate was evaluated using a continuous loading test of wheel rolling, and its load-bearing and buffering effects were investigated. Based on dynamic thermomechanical analysis, the microenergy-absorbing characteristics and damping behavior of the road maintenance energy-absorption seal were described, and its buffering mechanism was revealed. Finally, this study lays a solid foundation for the extensive investigation and promotion of the road maintenance energy-absorbing seal. The results show that the aggregate coverage rate is 40%, based on the seal surface texture and surface functions (wear resistance and sliding resistance). The ratio between the 2.36-4.75 mm and 1.18-2.36 mm aggregates is 25:75. The spraying plans for the energy-absorbing material are 1.0 and 2.0 kg·m-2 for the upper and lower layers, respectively. After 40 000 cycles of loading and wear cycles, the surface texture of the road maintenance energy-absorbing seal attenuated slightly, and the decline in the durability of its surface was evident. A road maintenance energy-absorbing seal can effectively reduce longitudinal and transverse strains at the bottom of an asphalt concrete plate. Moreover, it can convert the original tensile strain into compressive strain or decrease the value of the original tensile/compressive strain by over 30%-50%. The loss factor [tan(δ)] of the energy-absorbing seal is 0.1-0.3, and the seal can exhibit excellent damping performance within wide ranges of temperature (-50 ℃-200 ℃) and frequency (10-4-108 Hz).
  • Optimal Design for Double-layered Porous Asphalt Mixture Based on an Equivalent Layer Hydraulic Velocity Approach
    CAI Jun, HU Yu-ting, ZOU Peng-hui, LI Xi, QIAN Guo-ping, GU Fan
    China Journal of Highway and Transport. 2024, 37(10): 14-25. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.002
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    This study investigated the layer hydraulic characteristics of a double-layered porous asphalt (PA) pavement to better determine the critical design indices. A new two-directional permeameter was developed to measure the hydraulic velocity in the horizontal and vertical directions simultaneously. Based on the permeability test results, the influences of target air void, layer thickness, and nominal maximum aggregate size (NMAS) of mixture on the hydraulic velocity were systematically studied. Subsequently, a hydraulic velocity prediction model was established based on the XGBoost algorithm, and the significance of the influencing factors to hydraulic velocity was evaluated. After that, the bottom layer of a double-layered PA pavement from Suizimei Highway was redesigned based on the established model, which achieved the equivalent hydraulic velocity between top and bottom layers and kept layer thickness unchanged. Finally, the hydraulic velocity and critical service performance of the optimized PA were evaluated. The results indicated that the hydraulic velocity in the horizontal direction played a critical role in the hydraulic characteristic of PA pavement. In this study, the hydraulic velocity in the horizontal direction was greater than that in the vertical direction, even when the target air void increased to 21% with a test sample diameter of 150 mm. In addition, the hydraulic velocity in the horizontal direction was negligibly influenced by the factors including target air void, layer thickness, and NMAS of mixture. Second, the target air void is the most significant factor affecting the overall hydraulic characteristics of the PA mixture. Moreover, the layer thickness and NMAS also affected the hydraulic velocity, contributing as much as 25.2% and 18.5%, respectively. Thus, considering the layer thickness and NMAS into the mix design can significantly decrease the target air void of the bottom layer of a double-layered PA pavement while satisfying the hydraulic demand. Thereby, this optimization approach will help improve the service performance of a double-layered PA pavement.
  • Investigation of Fire Resistance of Fly Ash Blended Magnesium Phosphate Cement
    LIU Fei, PAN Bao-feng, ZHOU Chang-jun, WANG Bao-min, NIE Jia-yu
    China Journal of Highway and Transport. 2024, 37(10): 26-37. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.003
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    Magnesium phosphate cement (MPC) is a high-performance cementitious material that sets and hardens rapidly at room temperature. It is widely used for rapid repairs because of its high early strength, good durability, and strong bonding. Fly ash (FA) is often investigated in studies on solid waste applications because of its good chemical stability. In this study, the fire resistance properties of prepared FA blended magnesium phosphate cement (FA-MPC) were studied. The hydration product mechanism after high-temperature calcination was comprehensively analyzed using XRD, MIP, FT-IR, SEM/EDS, TGA, and DSC tests. The mechanical test results showed that with an increase in temperature, the compressive strength gradually decreased and then slowly increased. The compressive strength was 12.7 MPa at 900 ℃. The FT-IR results showed that the characteristic peak of crystalline water gradually disappeared with an increase in temperature. The XRD results showed that the crystal of K-struvite (MgKPO4·6H2O, MKP) lost crystal water in the process of high-temperature calcination. Then, the hydration products reached an amorphous state after 300 ℃, with no obvious crystal characteristic peaks. The FA-MPC system with MgKPO4 as the main crystal structure appeared in the FA-MPC after 600 ℃. The MIP test showed that the pore structure of the system changed significantly as the hydration product changed from a crystalline state to an amorphous state and finally reached a crystalline state. Finally, with the formation of the MgKPO4 crystal, the pore structure was compact, and the compressive strength of the FA-MPC was further improved. The thermogravimetric analysis results showed that the weight loss rate of the FA-MPC was approximately 1.1% after high-temperature calcination at 600 ℃, indicating that a stable system was formed at this time. The DSC results further showed that amorphous hydration products appeared at approximately 427 ℃.
    • Subgrade Engineering
  • Slope Displacement Prediction Using MIC-XGBoost-LSTM Model
    XU Jiang-bo, HOU Xin-min, WU Xiong, LIU Yi-fan, SUN Guo-zheng
    China Journal of Highway and Transport. 2024, 37(10): 38-48. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.004
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    A long short-term memory (LSTM) neural network model for predicting slope displacements based on maximum mutual information coefficients (MICs) and the XGBoost algorithm (MIC-XGBoost LSTM) was established to accurately predict slope displacements. First, the effects of different rainfall conditions on the slope were investigated. The maximum MIC was used to analyze the correlation between different rainfall conditions and the cumulative displacement of the slope, and the rainfall-influencing factors with significant correlations were determined. Next, based on the XGBoost algorithm, feature construction was performed on the influencing factors with high correlation using the cumulative displacement data of the slope, and the construction features were normalized with the original features. The normalized data were divided into training and validation sets. LSTM was used to predict the displacement of the Shangluo rock slope on the G312 National Highway. The XGBoost, LSTM, and MIC-XGBoost-LSTM prediction models were used to train and predict the cumulative displacement value of the slope, and the prediction accuracy was evaluated based on the root-mean-square error (RMSE), mean absolute error (MAE), and mean absolute percentage error (MAPE) indicators. In addition, the RMSE was used to determine the longest prediction cycle and minimum training sample size for the MIC-XGBoost LSTM model. Finally, the displacement data of the Baishui River landslide were used to further validate the model. The results show that the correlations between daily displacement increment, evapotranspiration, net rainfall, cumulative seven-day rainfall, and cumulative displacement at the monitoring point are higher than those of other factors, and the MIC of the feature values constructed using four related factors and the output feature values is 0.97. The RMSE, MAE, and (MAPE) of the predicted results obtained using the MIC-XGBoost-LSTM model are 0.25%, 0.185%, and 0.024%, respectively, which are lower than those of XGBoost and LSTM. Based on the RMSE, the longest prediction cycle and minimum training sample size of the MIC-XGBoost-LSTM model are 56 and 675, respectively. Finally, the displacement data of the Baishui River landslide were used for verification. The evaluation indicators are lower than those of the XGBoost and LSTM models, demonstrating that the MIC-XGBoost-LSTM slope displacement prediction model has high reliability.
  • Model Test Investigation on Mechanism of Road Collapse Induced by Underground Hydraulic Pipe Leakage
    DAI Zi-li, PENG Ling-hao, BAO Yang-juan
    China Journal of Highway and Transport. 2024, 37(10): 49-60. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.005
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    Road collapse is a typical geological disaster that threatens urban safety. To investigate the formation mechanism of road collapse, a model test apparatus is designed to understand the formation mechanisms of soil-erosion areas and collapse pits resulting from hydraulic pipeline leakage. The change characteristics of pore-water pressure and surface displacement caused by underground hydraulic pipeline extravasation are quantitatively analyzed using pore-water pressure and displacement sensors. The effects of four parameters on the soil-erosion process and the formation characteristics of collapse pits are investigated: the flow velocity of the pipeline water, the buried depth of the pipeline, the initial water content of the soil, and the defect position. The model experiment replicates the entire process of pavement subsidence induced by pipeline leakage, which can be classified into three stages: initial seepage, slow displacement, and stable erosion. The formation process of the conical erosion area above the pipeline defect and its influencing factors are analyzed. Based on observation, the erosion angle is independent of the initial moisture content of the soil, and as the pipeline burial depth increases, the flow speed within the pipeline decreases, thus consequently reducing the erosional angle. An equilibrium equation is derived for the sand-water blend in the fluidized erosion zone. The effects of these three parameters on the morphology of the collapse pit are discussed. The results show that the water-flow velocity inside the pipeline is positively correlated with both the depth and area of the collapse, and that a linear relationship exists between the pipeline burial depth and collapse width. The higher the initial moisture content of the sandy soil, the smaller is the collapse depth and the larger is the collapse area. The collapse depth is minimum when the defect is located at the bottom of the pipeline.
  • Particle Size Distribution Effect on Large-scale Triaxial Shear Mechanical Properties of Soil-rock Mixture
    ZHANG Chao, YU Jin, ZHU Dong-ping, GONG Jing-han, LI Zhe-han
    China Journal of Highway and Transport. 2024, 37(10): 61-72. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.006
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    Soil-rock mixtures are special geotechnical materials that have recently attracted considerable attention. It is very important to establish reasonable grading parameters (coefficient of nonuniformity Cu and coefficient of curvature Cc) to ensure the safety of high-fill embankments. To study the effect of particle size distribution on the shear mechanical properties of soil-rock mixtures, two groups of soil-rock mixture fillers were prepared. Group A had a constant value of Cc and a varying Cu, whereas group B had a constant value of Cu and a varying Cc. Large-scale triaxial compression tests were then performed to analyze the influence of the grading parameters on the deviatoric stress strength σf, initial deformation modulus Ei, cohesion c, and internal friction angle φ. Subsequently, the relationships between parameters K and n, ultimate deviatoric stress intensity (σ1-σ3)ult, and grading parameters were analyzed in conjunction with the Janbu empirical formula. Additionally, parameter determination methods for the Duncan-Chang model considering the influence of grading characteristics and stress state were proposed, and an improved Duncan-Chang model was established. Finally, the effects of the grading parameters on the particle structure and spatial distribution characteristics of the soil-rock mixture were determined, and three generalized models of matrix rock mass movement were proposed. The results show that the σf-Cu relationship curve exhibits a single peak, and the strength reduction after the peak value increases with increasing confining pressure. The σf-Cc relationship curve displays a linear increase, but gradually becomes convex and non-linear with an increase in the confining pressure. The Ei-Cu relationship curve exhibits a peak-valley alternating type, but gradually transitions to a single peak type with an increase in confining pressure. The Ei-Cc relationship curve shows a linear increase, with the average rate of change increasing in conjunction with the increase in confining pressure. The c-Cu relationship curve exhibits a level initial stage, followed by an increase. The c-Cc relationship curve shows a single valley and reaches its minimum value at Cc=1.74. The φ-Cu relationship curve displays a unimodal pattern and reaches its peak at Cu=10.0. The φ-Cc relationship curve is convex and nonlinear, exhibiting a maximum curvature at Cc=1.74. The improved Duncan-Chang model can effectively predict the failure process of large-scale triaxial shear deformation of a soil-rock mixture by considering the influence of the grading characteristics and stress state. The generalized model of the matrix-rock mass movement can effectively explain the large-scale triaxial shear mechanical properties of soil-rock mixtures caused by changes in the characteristics of the dense skeleton structure.
    • Bridge Engineering
  • System Reliability Analysis of Rail-road Double-deck Continuous Steel Truss Bridge
    WANG Chun-sheng, HE Wen-long, KOU Ting-wei
    China Journal of Highway and Transport. 2024, 37(10): 73-84. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.007
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    A system reliability analysis model is developed using an improved vector projection response surface method (IVPRSM) to enhance the efficiency and accuracy of calculating the static system dependability of long-span continuous steel-truss bridges. A novel approach was developed to enhance the efficiency of computing the component dependability index by optimizing the sampling process of the vector projection response surface technique. The limit state functions of steel truss bridge components can be effectively rebuilt, the design points can be promptly searched, and the failure probability of the components can be evaluated using the IVPRSM. The candidate failure components can be screened using the β-unzipping method. Considering the structural topology model was modified by assuming failure in the potential failure elements, the reliability indices of the remaining components were calculated using IVPRSM. Therefore, identifying the primary failure modes of steel-truss bridges and constructing a fault tree is possible. The structural system reliability index was determined using the differential equivalent recursion technique, which relied on the equivalent linear functions of the failure modes and the correlation coefficients between the failure modes. The efficacy and precision of the IVPRSM were confirmed through a reliability study of three numerical arithmetic cases. Considering a double-deck continuous steel truss bridge with a main span of 300 m as an engineering example, the proposed system reliability analysis method was used to calculate the reliability indices of the key components of the steel truss bridge in each failure stage. The study findings demonstrate that IVPRSM exhibits superior computational efficiency and accuracy compared with conventional approaches. At the ultimate limit condition of the load-carrying capacity, the reliability index for all types of critical members ranges from 4.1 to 4.8. The lower chord at the pivot of the main span of the truss girder, the upper chord and web member at approximately 1/4 of the main span (300 m), and the strengthened vertical bar in the center of the main span pose a significant danger of failure. Consequently, twenty primary failure modes affecting the load-carrying capability of the steel truss bridge were identified, resulting in a system dependability index of 4.6. This study proposes an IVPRSM-based reliability method for the static systems of continuous steel truss bridges. This algorithm may assist in designing continuous steel truss bridges by considering system reliability.
  • Flexural Performance of New Composite Beams with In-built Dowel Hot-rolled Steel and Ultra-high Performance Fiber Reinforced Concrete
    HE Yao-bei, SHEN Xiu-jiang, SHAO Xu-dong, CHEN Guang, ZHANG Yong-jian, WANG Xiao-ming, LI Wen-guang
    China Journal of Highway and Transport. 2024, 37(10): 85-97. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.008
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    To overcome the shortcomings that arise from the material properties and structural forms of traditional steel-concrete composite beams, a steel section with an in-built steel dowel ultra-high performance fiber-reinforced concrete (UHPFRC) composite beam is proposed suitable for regular-span bridges. Based on the trial design of a 3×30 m continuous beam on a highway in Hunan province, a flexural experiment was conducted on a 1:1.85 scaled model under positive bending moments. Subsequently, digital image correlation (DIC) analysis was performed to discuss the failure modes, initiation and propagation of microcracks, and strain distribution patterns of the tested beam. The test results were validated using theoretical and finite element analysis (FEA). The results show that the steel dowel connector ensures effective interaction between steel and UHPFRC components. The composite beam failed in the flexural failure mode with obvious ductility, and the entire section of the steel component almost yielded. The flexural behavior of the composite beam can be characterized into five domains: elastic, quasi-elastic, microcrack propagation, main crack formation, and softening. The new composite beam was characterized by superior crack resistance. The microcracks in the tensile zone of the UHPFRC web developed only after the steel component yielded. A sectional analysis that considers the UHPFRC tensile contribution can accurately predict the flexural response of the new composite beam.
  • Spanwise Layout Optimization of Aerodynamic Countermeasures Against Torsional Vortex-induced Vibration on Huangmaohai Bridge
    SUN Hao, GUO Guo-he, ZHU Qing, ZHU Le-dong, TAN Zhong-xu, QUAN Hong-lie
    China Journal of Highway and Transport. 2024, 37(10): 98-106. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.009
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    Wind tunnel tests on a large-scale sectional model of the Huangmaohai Bridge indicated that torsional vortex-induced vibration (VIV) of its deck can be suppressed by partially closing its railings. However, installing such aerodynamic countermeasures along the entire span of the bridge deck could significantly increase the lateral wind load. To determine the minimum required installation length of aerodynamic countermeasures and the corresponding installation locations along the span, the parameters of a nonlinear vortex-induced force (VIF) model for bridge deck sections with and without aerodynamic countermeasures were identified using wind tunnel tests. The VIF model was subsequently applied to conduct a mode-by-mode analysis of the VIV response of a prototype bridge with countermeasures. Finally, the spanwise layout of the aerodynamic countermeasures was optimized considering the constraint of a limited VIV response on the bridge. The results indicate that the partial closure of the railings suppresses the torsional VIV of the bridge deck section by reducing the negative aerodynamic damping effect of the VIF. However, installing such countermeasures over an entire span is overly conservative; the total installation length of aerodynamic countermeasures can be significantly reduced by optimizing their spanwise layout using the proposed method.
  • Local Stiffness Theory of Damper Parameter Optimization for Cable Vibration Control
    YU Jian-da, LIU Yun-yan, PENG Wen-lin, CHEN Zhi
    China Journal of Highway and Transport. 2024, 37(10): 107-115. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.010
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    Currently, a common method for suppressing cable vibrations is installing a viscous damper near the anchor end of a cable to improve the cable damping ratio. However, a small damping coefficient cannot consume sufficient energy, and a large damping coefficient has an obvious clamping effect on the cable, causing the cable to produce excessive local deformation and reducing the damper stroke. Meanwhile, local deformation can reduce the energy consumption efficiency of the dampers. Therefore, optimization design of the damping parameters for the cable-viscous damper is an important step towards ensuring the damping effect, which can improve the additional damping ratio of the cable. To this end, local stiffness is used to simulate the clamp-tightening effect of the damper on the cable, and the local stiffness theory is proposed to calculate the additional damping ratio of the cable. The local stiffness of the cable was calculated considering the cable length, damper installation position, cable force, and average amplitude. In addition, the vibration equation of the cable-viscous damper system can be derived from the single-mode shape, and the analytical solution of the additional damping ratio of the viscous damper for the vibration damping of the cable can be obtained. The calculation results indicate that for the first four modal additional damping ratios of the small sag cable, the local stiffness theory is consistent with the classical theory. After considering the eddy-current damper as the energy-dissipating element, a damping model test of the cable-viscous damper was conducted, and the first modal additional damping ratio of the cable was obtained under the condition of three cable tensions with large differences. The measured results are in good agreement with the analytical solution, verifying the accuracy of the local stiffness theory for predicting the additional damping ratio of different sag cables. The maximum additional damping ratio and optimal viscosity coefficient of any mode of the cable with different sags can be obtained by single-mode analysis in the theory of local stiffness, which has the advantage of clear physical significance and easy calculation. This study provides a practical method for calculating the actual projects.
  • Study of Interfacial Bond Between Carbon Fiber Reinforced Polymer Plates and Steel Under Large Temperature Difference Cycles Action
    REN Xiang, ZHANG Ze-ya, SUN Ya-min, HAN Xiu-zhu, CHEN Shao-jie, ZHOU Hao-nan
    China Journal of Highway and Transport. 2024, 37(10): 116-127. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.011
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    In a thermal cycling environment, the bonding interface of carbon fiber-reinforced plastics (CFRP) (commonly used to reinforce steel structures) is adversely affected. To investigate the influences of large temperature difference cycling on the bonding performance of CFRP-strengthened cracked steel specimens, adhesive specimens, and CFRP-steel specimens were fabricated. The highest and lowest temperatures for the cyclic thermal conditions were set to 60 ℃ and 25 ℃, respectively. Environmental and tensile tests were conducted on the adhesive specimens and CFRP-steel specimens to analyze the failure modes, load capacity, interfacial shear stress distribution, and bonding-slip relationship. The results indicate that, during the initial stages of large temperature difference cycling, the tensile strength and elastic modulus of the adhesive exhibit a slight increase. However, as the number of cycles increases, the ultimate load, peak interface shear stress, stiffness, and fracture energy of both the adhesive and CFRP-steel specimens progressively decline. The CFRP-steel specimens primarily display a mixed failure mode involving interface peeling and fiber delamination, with no descending sections in the load-displacement and bond-slip curves, reflecting brittle failure characteristics. In conclusion, large temperature difference cycling not only reduces the adhesive layer strength at the CFRP-steel interface but also diminishes the bond performance between the adhesive, CFRP plates, and steel plates. These two factors are the main contributors to the reduction in load-bearing capacity of the CFRP-steel specimens. Based on the bond-slip parameters of the CFRP-steel interface, a degradation model of the bond-slip relationship was established, allowing for the prediction of the interface shear stress and slip under temperature cycling. This provides valuable insights for enhancing the durability of reinforcement designs.
  • Experimental and Analytical Model for Deformation Characteristics of a Cyclic Laterally Loaded Pile in Sloping Ground
    ZHANG Ling, YUE Shao, ZHAO Ming-hua, LI Qiong, PENG Wen-zhe
    China Journal of Highway and Transport. 2024, 37(10): 128-138. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.012
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    The deformation characteristics of piles under cyclic lateral loading (such as vehicle, wind, or wave loads) in sloping ground are extremely complex. This study accordingly conducted cyclic lateral loading tests of model piles in sandy ground with different slope angles and compared the deformation results with those of static load tests to analyze the cumulative deformation characteristics of the piles. The deformation calculation method was subsequently modified to account for the effective depth reduction using a reduction factor defined as a function of the change in the tangent of the slope, tan(θ). Next, a matrix transfer method for calculating the stress and deformation behavior of piles in sloping ground under cyclic lateral loading was proposed and applied to conduct a preliminary analysis of the depth of influence of the cyclic effect and the cyclic weakening law according to the scale factor m for each slope. The results indicate that the cyclic load-displacement curves of the piles at each slope angle are characterized by significant displacement accumulation and non-linear hysteretic energy dissipation; the slope effect further amplifies the accumulated displacement under the cyclic effect; the cumulative displacement is characterized by a three-stage variation with the number of cycles N according to the power function a(θ)Nb; the value of m varies in three stages with N in the same manner as the cumulative displacement; and there is a cyclic effect on the depth to which the value of m is influenced.
    • Tunnel Engineering
  • Model for Calculating Longitudinal Bending Stiffness of Shield Tunnels Considering Reduction in Longitudinal and Transverse Stiffnesses
    YE Xiao-wei, WEI Yu-jun, CHEN Yun-min, FAN Yi-xiong
    China Journal of Highway and Transport. 2024, 37(10): 139-150. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.013
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    Joint bolts reduce the longitudinal and transverse bending stiffnesses of shield tunnels. Based on the classical longitudinal equivalent continuous beam theory for shield tunnels, as well as considering the reduction effect of the transverse bending stiffness of shield segments and the combined action of axial force and bending moment, this study proposes a model for calculating the longitudinal bending stiffness of shield tunnels based on an elliptical cross-section and a strict elliptical-integration derivation. The governing equation of the proposed model is a transcendental equation, and a numerical method is used to solve the governing equation. The proposed model is compared with existing models derived from circular and elliptical cross-sections, but not strictly elliptical integration. Additionally, the effects of the transverse bending stiffness of shield segments and the material stiffness of shield segments and joint bolts on the longitudinal equivalent bending stiffness of shield tunnels are analyzed. The findings show that for a circular cross-section, the results of the proposed model are consistent with those of existing models. Existing models derived based on a circular cross-section are specific cases of the proposed model; when the geometric and material parameters are provided, the longitudinal equivalent bending stiffness of shield tunnels and the ratio between the axial force and bending moment present nonlinear and positive correlations within the range of positive and negative critical ratios between the axial force and bending moment. The longitudinal equivalent bending stiffness is constant outside the range of positive and negative critical ratios between the axial force and bending moment. Meanwhile, it decreases with the transverse bending stiffness of the shield segments or the material stiffnesses of the shield segments and joint bolts. These findings provide a theoretical reference for the longitudinal-deformation analysis of shield tunnels.
  • Thermal Storage Antifreeze System and Its Influencing Factors Analysis in High Cold-region Tunnel
    ZHANG Yao, XIA Cai-chu, PENG Wen-bo, ZHANG Jian-xin, HU Yun-jin
    China Journal of Highway and Transport. 2024, 37(10): 151-161. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.014
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    To economically and effectively solve the problem of freezing damage in high cold-region tunnels, a new type of heat storage antifreeze system for tunnel surrounding rock was proposed and applied to the Tianshan Shengli Tunnel of Wuwei Expressway in Xinjiang, considering heat storage and frost protection in tunnel entrance. A three-dimensional heat storage coupled heat transfer model for tunnel surrounding rock was established, and the heat storage capacity and model reliability of the system were confirmed through comparison with on-site heat storage and heat response test data. The thermal storage characteristics of the tunnel surrounding rock and its antifreeze effect were investigated, and the influences of inlet temperature, pipe spacing, and operating state on the heat storage power and antifreeze effect of the system were analyzed. The results show that when the inlet temperature is 35 ℃ and the heat storage operation is 60 days, freezing damage does not occur at the entrance of the Tianshan Shengli Tunnel. Both the heat storage power and the temperature behind the secondary lining increase linearly with an increase in the inlet temperature: when the inlet temperature increases to 40 ℃, the antifreeze effect of the system increases by 14.55%. The smaller the pipe spacing between the heat storage pipes, the more conducive to the temperature increase behind the secondary lining and the antifreeze effect, when the pipe spacing is reduced from 0.46 to 0.3 m, the temperature behind the secondary lining increases from 18.86 to 24.12 ℃, and the antifreeze effect significantly increases by 27.89%. Intermittent operation during the heat storage period contributes to improvement in the efficiency of the heat storage system, and the longer the duration of the heat storage operation, the more favorable it is for anti-freezing. The research results provide theoretical methods and technical support for heat storage and frost prevention systems of the surrounding rock in high-cold-region tunnels.
  • Effect of Segment Ring Opening of Shield Tunnel on Its Longitudinal Bending Rigidity
    HUANG Da-wei, LI Qing, CAI Guo-qing, JIANG Hao, LUO Zhong-rui
    China Journal of Highway and Transport. 2024, 37(10): 162-170. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.015
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    After the completion of the shield tunnel, owing to certain functional requirements, opening at different positions of the shield tunnel, such as the construction of the channel connecting the two parallel shield tunnels, the construction of the underground shaft pump room at the bottom of the shield tunnel, and the construction of the shaft at the top of the shield tunnel are necessary. This study sets up three different openings at the same position of the shield tunnel: the top, side, and bottom openings. To resolve the problem caused by the reduction in the longitudinal rigidity of shield tunnel after opening, which is prone to longitudinal uneven settlement or horizontal deflection deformation, a model shield tunnel with a geometric similarity ratio of 1:10 was designed, and the influence of openings at different positions of the shield tunnel on its longitudinal rigidity was carried out. The simply supported beam method was used to compare and analyze the measurements of the openings at different positions of the shield tunnel and unopened tunnel. The influence of the opening extent of the annular joint, opening position, and opening at different positions on the longitudinal bending rigidity of the model tunnel were analyzed. The bending rigidity of the tunnel in different directions after opening was tested. The results show that rigidity decreases by 90.5% when the opening position is compressed, 64.6% when the opening position is tensioned, and 42.4% when the bending direction of the tunnel is perpendicular to the opening position. After the opening of the shield tunnel, the bending rigidity of the shield tunnel is reduced owing to the removal of the ring joint connection bolts at the opening. In the bending process of the relatively complete shield tunnel, the corresponding rigidity at different openings plays different roles; therefore, the degree of rigidity reduction of the shield tunnel varies. After the shield tunnel is opened, the bending rigidity of the tunnel is related to its bending direction and the relative position of the opening. In the analysis of the load deformation and seismic analysis of the shield tunnel, the bending rigidity of the shield tunnel should be determined according to the bending direction of the tunnel.
    • Traffic Engineering
  • Combined with Machine Learning and Ordered Logistic Regression for Pattern Recognition and Safety Analysis in Pedestrian-vehicle Crossing Interaction at Unsignalized Crosswalks
    YAN Ying, ZHOU Mo, YUAN Hua-zhi, DONG Shuai, CHEN Xin-qiang
    China Journal of Highway and Transport. 2024, 37(10): 171-183. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.016
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To investigate the impact of the behavioral preference and dynamic spatio-temporal relationship of pedestrian-vehicle interaction (PVI) on potential traffic conflict, a safety analysis approach incorporating machine learning and ordered logistic modeling is proposed. The pedestrian-vehicle crossing data at unsignalized crosswalks was collected through unmanned aerial vehicle (UAV). The 876 pairs of PVI were extracted from of trajectories road users. Considering the dynamics of interactions, the interaction indicators based on competition for right-of-way and collision relationships were proposed. A representation learning model was trained to capture time-series data of PVI, transformed these into potential representations, and clustered them to identify and analyze typical interaction patterns and features. Utilizing these patterns and varying conflict severities, multiple ordered logistic models were developed to investigate the factors influencing conflict risk and to explore differences in risk causation across distinct interaction patterns. The findings reveal that PVI can be categorized into three distinct patterns: near-interaction, far-soft-interaction and far-hard-interaction; Reductions in relative pedestrian-vehicle distances, increases in lower vehicle speed limits and upper pedestrian speed limits are common factors that reduce conflict severity; For near-interactions, rapid pedestrian deceleration, right-of-way competition, and high-speed vehicles reduce conflict risk, and both extreme vehicle deceleration and rapid pedestrian acceleration increase the danger; For far-interactions, an increase in the pedestrian speed lower limit leads to an increase in conflict risk; Rapid vehicle deceleration and right-of-way competition reduce the conflict risk for far-soft-interactions; Pedestrian sharp deceleration and high-speed vehicles are the main factors that reduce the conflict risk of far-hard-interactions, while pedestrian sharp acceleration raises the danger. The application of the combined approach reduces the influence of the heterogeneity of PVI behavior on the analysis results. The conclusions of the study provide a theoretical basis for enhancing safety in pedestrian crossing on urban roads.
  • Car-following Behavior Modeling and Simulation Verification Considering Distribution Uncertainty and Correlation
    WU Shu-bo, ZOU Ya-jie, ZHONG Xin-zhi, ZHANG Yun-long, TANG Shu-ning
    China Journal of Highway and Transport. 2024, 37(10): 184-195. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.017
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    The accurate analysis of the parameter characteristics of car-following models improves the accuracy and reliability of microscopic traffic simulations. To simultaneously consider the distribution uncertainty and correlation of car-following model parameters, this study proposes a modeling method based on the Bayesian model averaging Copula (BMAC) to describe car-following behavior characteristics. Car-following event trajectories were extracted from the HighD naturalistic driving dataset and the parameters of the Gipps model, intelligent driver model (IDM), full velocity difference model (FVDM), and longitudinal control model (LCM) were calibrated. The BMAC approach was employed to model the parameter calibration results statistically, and the advantages of various distributions were leveraged to overcome the issue of distribution uncertainty and capture parameter correlations. In this study, a series of repeated numerical simulations were conducted to validate the effectiveness of the BMAC approach. The experimental results demonstrate that distribution uncertainty and correlation exist among the parameters of the car-following models. However, the BMAC approach can capture parameter correlations and address the issue of parameter distribution uncertainty to provide more accurate descriptions of car-following behavior characteristics. The parameter sampling method based on BMAC (denoted as BCCO) achieved the best simulation performance, achieving the lowest average Kolmogorov-Smirnov (K-S) statistics for the time to collision, speed, and spacing among the four car-following models. Taking the LCM as an example, the average K-S statistics for the time to collision, speed, and spacing were 0.231, 0.310, and 0.294, respectively. Therefore, the proposed BMAC-based parameter sampling method effectively enhances the realism of microscopic traffic simulations and provides accurate simulation evaluation results for traffic management and control strategies.
  • Analyzing Congestion Characteristic of Expressway Network from Perspective of Resilience
    XU Peng-cheng, LU Qing-chang, LI Jing, WANG Shi-xin, REN Yong-quan, ZHANG Wei
    China Journal of Highway and Transport. 2024, 37(10): 196-208. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.018
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Congestion is a common phenomenon that affects the operational performance of expressway networks. However, previous studies have focused on congestion delays in regional road networks due to section failures within a short period of damage, whereas the effect of dynamic congestion caused by macro-traffic flow fluctuations is disregarded. To address the characteristics of road-network resilience based on the generation-cluster-recovery process of dynamic congestion, this study integrates network topology, spatiotemporal characteristics of dynamic flow, and road-infrastructure attributes to devise a percolation-theory-based methodology for the congestion resilience of expressway networks. This approach was demonstrated and analyzed in the expressway network of a province in China. The results show that the road-network resilience and congestion cluster scale demonstrate an approximate power distribution and a scale-free law under different spatiotemporal conditions. Under speed thresholds (ql) of 0.2 and 0.7, the congestion cluster reaches the transition state and the road-network resilience is reduced by approximately 65%. Comparing the resilience curves for different time periods, the congestion recovery time of evening peak hours is approximately 50% higher than that of other periods. Additionally, the transportation infrastructure type significantly affect the congestion resilience of road networks. The recovery time of congested bridges and tunnels is 25% longer than that of normal sections. When the proportion of bridges and tunnels exceeds 65%, the road-network resilience decreases by approximately 50% under different spatiotemporal conditions. The findings of this study could provide the theoretical evidence and practical implications for traffic management to mitigate and prevent frequent congestion.
    • Automotive Engineering
  • End-to-end Autonomous Driving: Advancements and Challenges
    CHU Duan-feng, WANG Ru-kang, WANG Jing-yi, HUA Qiao-zhi, LU Li-ping, WU Chao-zhong
    China Journal of Highway and Transport. 2024, 37(10): 209-232. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.019
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    End-to-end autonomous driving methodologies eliminate the need for manually defined rules and explicit module interfaces. Instead, these approaches directly map trajectory points or control signals from raw sensor data, thereby addressing the inherent shortcomings associated with traditional modular methods, such as information loss and cascading errors, and overcoming the performance limitations imposed by rule-driven frameworks. Recent advancements in self-supervised-learning-based generative artificial intelligence have exhibited substantial emergent intelligence capabilities, significantly promoting the evolution of end-to-end methodologies. However, the existing literature lacks a comprehensive synthesis of the advancements in generative end-to-end autonomous driving. Consequently, this paper systematically reviews the research progress, technical challenges, and developmental trends in end-to-end autonomous driving. Initially, the input and output modalities of the end-to-end models are delineated. Based on the historical progression of end-to-end autonomous driving, this paper provides an overview and comparative analysis of the foundational concepts, current research status, and technical challenges of traditional, modular, and generative end-to-end methods. Subsequently, the evaluation methodologies and training datasets utilized for end-to-end models are summarized. Furthermore, this paper explores the challenges currently faced by end-to-end autonomous driving technologies in relation to generalization, interpretability, causality, safety, and comfort. Finally, predictions are made for the future trends of end-to-end autonomous driving, emphasizing the fact that edge scenarios provide critical support for the training of end-to-end models, which can enhance the generalization capabilities. In addition, self-supervised learning can effectively improve training efficiency, personalized driving can optimize user experience, and world models represent a pivotal direction for the further advancement of end-to-end autonomous driving. The findings of this research serve as a significant reference for refining the theoretical framework and enhancing the performance of end-to-end autonomous driving systems.
  • Fault Diagnosis of Power Battery System for Electric Vehicles Based on Optimized Entropy Algorithm in Real Scenarios
    LIU Qi-quan, MA Jian, ZHAO Xuan, ZHANG Kai, MENG De-an
    China Journal of Highway and Transport. 2024, 37(10): 233-248. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.020
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Fault diagnosis of power battery systems is key to ensuring the safe and reliable operation of electric vehicles, in which the avoidance of false alarms not only reduces the driver's anxiety regarding vehicle safety but is also necessary for the practical application of the diagnostic method. Therefore, it is crucial to improve the reliability of the method. Abnormal voltage fluctuations in a power battery system are critical signals released by the deterioration of battery performance; hence, entropy methods, which can satisfactorily assess the degree of data dispersion, have been widely studied in battery fault diagnosis. However, when the classical Shannon entropy method based on interval probability was validated in engineering practice, many primary and secondary false-alarm single cells were found in the results. Vehicle voltage data with thermal runaway accidents were first used to analyze the fault diagnosis principle of the model to improve the accuracy of the method. Furthermore, based on normal vehicle operation data, the false-alarm mechanisms of the model in two typical scenarios were investigated. Under the above conditions, two measures were proposed to mitigate the false and missing alarm problems of the original method: the data optimization method and the kernel density estimation and entropy fusion method. Finally, real fault samples with different fault characteristics were selected to test the generalization ability of the algorithms, and their validity and reliability were verified separately. Based on a large amount of normal in-service vehicle data, a comparative analysis of the performance before and after model optimization was conducted. The results show that the relative false alarm rates of the two methods on normal vehicles decrease by 90% and 98%, respectively. Thus, this study significantly improves the reliability of the diagnostic strategy, promotes the online real-vehicle application of the methods, and provides ideas for analyzing and optimizing the accuracy of other fault diagnostic strategies.
  • Multi-task Integrated Driving Decision and Control Method Oriented to Driving Demands
    HAN Yu, MA Xiao-lei, TAO Yan-meng, YU Bin
    China Journal of Highway and Transport. 2024, 37(10): 249-266. https://doi.org/10.19721/j.cnki.1001-7372.2024.10.021
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The integration of various driving tasks and demands has become a trend in the decision-making and control technology of autonomous vehicles. However, expanding driving conditions generate significant conflicts between demand indicators, posing greater challenges to algorithmic efficiency. To address this problem, this study proposes a real-time method based on nonlinear model predictive control theory. The proposed method features multiple driving functions and satisfies multiple requirements. An indicator scheduling strategy based on driving demand priority was first designed to handle the conflict between demand indicators and dynamically adjust the integration method of the indicators. Two indicator functions were next established based on frequency response analysis to balance calculation accuracy and complexity. An adaptive Lagrange discretization method was then designed to ensure control accuracy with fewer discrete points. Simulations and experiments validate the ability of the proposed method to achieve multiple tasks under normal and emergency driving conditions, satisfy performance requirements, and solve algorithms in less than 50 ms. The results present a novel perspective for improving real time efficiency of planning algorithm.
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