公路交通科技

05 December 2025, Volume 42 Issue 12
    

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  • Mixed traffic flow model based on driving risk pulse field
    ZHANG Yin, SHUAI Bin, FAN Chengjing, NIU Yifan, HUANG Wencheng
    2025, 42(12): 1-10. https://doi.org/10.3969/j.issn.1002-0268.2025.12.001
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    [Objective] This study aims to clarify the influence of connected and automated vehicles (CAVs) adoption on road traffic flow. It seeks to understand mixed traffic flow operation patterns, identifying traffic conditions beneficial for CAVs development. Studies on car-following models and fundamental diagram models are needed. These models should address mixed traffic of CAVs and human driving vehicles (HDVs). [Method] First, risk energy was introduced to characterize vehicle threat capability. Based on risk pulse and risk pulse field theory, a driving risk pulse field was established. This field described risk distribution. Then, a car-following model was developed, matching CAVs perception and interaction capabilities. It combined with FVD model to form a mixed traffic flow car-following model. The mixed traffic flow fundamental diagram model was derived. Finally, simulations were conducted on traffic flow fundamental diagrams with different CAVs penetration rates and different vehicle type compositions. The influence of CAVs adoption on road capacity was studied. Corresponding traffic administration suggestions were obtained. [Result] Road maximum capacity increases with higher CAVs penetration rates. Optimal equilibrium speed also increases. The degree of capacity improvement depends on traffic composition. When CAVs penetration reaches 100%, the road maximum capacity increases from 2 320 veh/h to 3 060 veh/h. The corresponding optimal equilibrium speed increases from 16 m/s to 19 m/s. Introducing 45% threatening vehicles reduces road capacity by approximately 17.5%. [Conclusion] Reasonable management measures should be adopted. Different types of traffic flows should be separated. Road equilibrium speed should be controlled. These measures will better utilize the advantages of CAVs.
  • Short-time traffic flow prediction based on hybrid model of CEEMDAN and optimized CNN-BiLSTM
    LI Wenhan, YANG Qi, DAI Zhikang, YANG Xiaolei, WEI Yutong
    2025, 42(12): 11-23. https://doi.org/10.3969/j.issn.1002-0268.2025.12.002
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    [Objective] Short-term traffic flow prediction accuracy is insufficient due to urban road network expansion and diverse traffic conditions. This study proposes a hybrid prediction model CNN-BiLSTM, combining with CEEMDAN signal decomposition and improved gray wolf optimization (IGWO) algorithm. [Method] First, raw traffic flow data were decomposed to 15 IMF components and one residual term by using CEEMDAN. It effectively separated multi-frequency intrinsic mode functions and removed noise, overcoming mode aliasing problems in the traditional EMD model. Second, the hyperparameters, e.g., convolutional layer numbers, convolution kernel numbers, BiLSTM neuron numbers, and pooling layer stride, of CNN-BiLSTM network were optimized with IGWO. Finally, each IMF and residual component was input the optimized CNN-BiLSTM model for prediction. The final prediction result was obtained by summing all individual outputs. [Result] The proposed CEEMDAN-IGWO-CNN-BiLSTM model has significant improvements over the standard CNN-BiLSTM model. MAE drops by 58.04%; MAPE decreases by 57.86%; RMSE declines by 57.66%. [Conclusion] The proposed model could effectively capture temporal dependencies, periodicity, and noise in traffic flow data, providing traffic administration departments with precise insights into traffic dynamics. It enables better traffic flow allocation and enhances transportation efficiency. The study confirms the effectiveness of CEEMDAN decomposition and IGWO optimization for short-term traffic prediction. These techniques offer new solutions for ITS, addressing urban congestion and improving road network performance.
  • Key factors coupling in hazardous materials road transport accidents integrating higher-order network and functional resonance analysis method
    REN Cuiping, LI Xiaofei, XIE Fengjie
    2025, 42(12): 24-36. https://doi.org/10.3969/j.issn.1002-0268.2025.12.003
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    [Objective] Identifying key factors is a crucial approach to curbing accidents, playing a decisive role in accident occurrence. Meanwhile, the coupling effects among these key factors not only exacerbate accident development, but also exert significant influences on accident evolution and consequences. To accurately identify key factors and quantitatively characterize their coupling relations, this study takes hazardous materials road transport accidents as the study object and proposes a coupling analysis method integrating higher-order networks (HON) and functional resonance analysis method (FRAM). [Method] First, the key accident nodes and their interaction networks were extracted based on overlapping community detection in the high-order network of accident causes, constructing HON-FRAM model among key nodes. Second, the performance variation and potential coupling relations among nodes were quantitatively analyzed to identify links vulnerable to coupling mutations and their interaction mechanisms. Finally, an empirical analysis was conducted by using hazardous materials road transport accidents that occurred in China from 2017 to 2021. [Result] Ten high-coupling functional failure and fracture links exist in the hazardous materials road transport system. Among these, human factors and vehicle functions are key causal functions prone to forming failure chains. Improper operation is the primary human-induced cause of accidents. Collisions and rollovers are the high-coupling initial accident nodes most likely to trigger secondary accidents, while tank damage serves as a critical transfer node in accident evolution. [Conclusion] The established model effectively simulates the interaction mechanisms among key factors in hazardous materials road transport accidents, identifying critical causal factors and their high-coupling links.
  • Emergency lane change obstacle avoidance and stability control for hub motor vehicles based on risk prediction
    FU Xiang, WANG Wenju, WAN Jiaqi, WANG Jia, PEI Chao
    2025, 42(12): 37-49. https://doi.org/10.3969/j.issn.1002-0268.2025.12.004
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    [Objective] This study aims to ensure obstacle avoidance safety, vehicle stability, and trajectory accuracy for hub motor intelligent vehicles during high-speed emergency lane change. The path planning and tracking control strategy were proposed based on lane change risk prediction. [Method] First, a dual fuzzy dynamic identification model was developed to assess the driving environment and predict lane change risk. This model determined whether a lane-change was necessary for obstacle avoidance. Second, a fifth-degree polynomial-based path planning algorithm was introduced. Lagrange multiplier method was applied to generate the optimal trajectory. Third, a model-based predictive tracking controller was designed for lateral displacement tracking to improve path tracking accuracy. An optimized integral sliding mode controller was developed to enhance lateral stability during path tracking. It minimized the desired parameter deviations, and computed the required yaw compensation torque. Additionally, an adaptive fuzzy PI controller was designed to maintain the stable longitudinal speed during obstacle avoidance. It determined the necessary longitudinal adjustment torque. Finally, the torque distribution for each hub motor was regulated based on torque constraints in both lateral and longitudinal directions. [Result] At 72 km/h, the lateral tracking error was within 0.18 m, the steady-state error was within 4.3%, the obstacle avoidance time was 1.5 s, and the longitudinal speed deviation was within 0.12 m/s. At 100 km/h, the lateral tracking error remained below 0.46 m, and the vehicle stability was restored within 2.3 s. In contrast, the comparative control strategy failed to maintain stability in high-speed conditions. [Conclusion] The proposed control strategy effectively avoids obstacles at medium and high speeds. It maintains vehicle stability and trajectory tracking accuracy during avoidance, thereby improving lane change safety.
  • System dynamics based prediction on Guangdong-Hong Kong cross-border highway traffic flow
    XIAO Sheng
    2025, 42(12): 50-58. https://doi.org/10.3969/j.issn.1002-0268.2025.12.005
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    [Objective] This study developed a traffic flow prediction model based on system dynamics theory to scientifically predict the future scale of Guangdong-Hong Kong cross-border highway traffic flow, as well as improve the scientific nature of transport infrastructure planning decisions. [Method] First, the cross-border highway transport was divided into categories of passenger and freight. A diagram of systematic causality was formed. It analyzed the correlation between the flow of cross-border passenger vehicles and the economic development, population size, vehicle factors, respectively; and analyzed the correlation between the flow of cross-border trucks and Guangdong-Hong Kong trade, port freight, life necessities supply demand from mainland to Hong Kong, respectively. Second, the system flowchart and dynamic equations were constructed by using Vensim PLE software. A system dynamics model of Guangdong-Hong Kong cross-border highway traffic flow was established. The model accuracy was verified through simulation based on the measured data from 1999 to 2019. Finally, the scenario analysis was conducted in low, medium, and high growth conditions to predict the cross-border highway traffic flow up to 2035. [Result] The simulation result indicates that the system dynamics model achieves a prediction error within ±6.5%, confirming its reliability. The prediction result indicates that the daily cross-border highway traffic flow will reach 54 600 vehicles in the low growth scenario, 71 000 in the medium growth scenario, and 218 000 in the high growth scenario by 2035. The traffic flow of passenger vehicles grows much faster than freight, and becomes the main driver of total growth. [Conclusion] The system dynamics based prediction method is practical and adaptable. It overcomes the limitations of traditional models that fail to capture complex cross-border interactions. The findings provide a scientific basis for planning new cross-border highways, improving traffic facilities, and formulating future transport policies between Guangdong and Hong Kong.
  • Ambient air-based asphalt mixture density measurement method and its traceability analysis
    CAI Jiacheng, HE Tianqing, ZHANG Bing, LIU Lu, XIA Huisen, LI Jian
    2025, 42(12): 59-67. https://doi.org/10.3969/j.issn.1002-0268.2025.12.006
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    [Objective] This study proposed ambient air-based asphalt mixture density measurement method for improving measurement convenience, and designed experiments to evaluate its measurement uncertainty. [Method] First, a measurement model was established based on the ideal gas law. In isothermal conditions, the pressure increment and amount-of-substance increment of air flowing into evacuated chamber were monitored to accurately calculate the chamber’s vacant volume. The specimen density was determined by using the known total chamber volume and the mass measured with high-precision balance. Subsequently, the asphalt core samples were measured to validate the proposed method, and systematically compared with those by using surface dry method. Furthermore, a series of wax-sealing comparative tests were specifically designed and conducted to investigate the sources of bias with traditional methods. Finally, the standard specimens with specific internal structures were designed to precisely evaluate the proposed method’s performance and analyze the influence of open pores. The comparative traceability tests alongside uncertainty analysis were performed against the water displacement method. [Result] The correlation coefficient was 0.99 between the proposed method and surface dry method. The proposed method was less susceptible to operational variability. Notably, for specimens with large internal voids and small openings, the proposed method reduced volume and density measurement errors by 9.0 cm3 and 0.048 g/cm3 respectively, compared with conventional methods. [Conclusion] The expanded uncertainty with single density measurement by using the proposed method reaches 0.028 g/cm3. The process does not rely on rare gases, and the results are unaffected by the morphology of open pores, achieving high-precision, portable, and automated measurement of asphalt mixture density parameters.
  • Uniaxial compression constitutive model of cement stabilized macadam under temperature-salt coupling
    TANG Ke
    2025, 42(12): 68-76. https://doi.org/10.3969/j.issn.1002-0268.2025.12.007
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    [Objective] This study investigated the stress-strain curve characteristics and constitutive model of cement stabilized macadam under temperature-salt coupling, as well as revealed its mechanical response characteristics and deformation mechanism. [Method] Based on the existing uniaxial compression constitutive model of concrete, the influences of different temperatures and cement contents on macadam mechanical properties were studied through the uniaxial compression tests. Based on the least squares fitting and normalization processing, the constitutive model of cement stabilized macadam was proposed to characterize its uniaxial compressive mechanical response and deformation mechanism under temperature-salt coupling. [Result] The stress-strain curve of cement stabilized macadam was basically the same as that of concrete under the influences of temperature and sodium sulfate. The curve showed three typical phases, i.e., straight rising section, curved rising section and curved falling section. The classical stress-strain constitutive model of Zhenhai Guo was modified based on the characteristics of curves variation. The parameters, reflecting influences of temperature-salt coupling, were introduced. The uniaxial compression constitutive model of cement stabilized macadam suitable in sodium sulfate corrosion condition was successfully constructed. [Conclusion] The established uniaxial compression constitutive model under temperature-salt coupling reveals the mechanical response rule and deformation mechanism of materials by using the least squares method and data normalization processing method. It would provide a theoretical basis for the study on multi-axial damage constitutive model of cement stabilized macadam materials.
  • Influence of centrifugal model test loading on mechanical deformation of pile-supported embankment
    JIANG Yanbin, LUO Xian, WANG Zhangchun, WANG Yanfang, FAN Wenhu
    2025, 42(12): 77-85. https://doi.org/10.3969/j.issn.1002-0268.2025.12.008
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    [Objective] Centrifugal model tests for pile-supported embankment often use the method of increasing centrifugal acceleration (g-rising) to simulate the embankment loading process; however, the influence of this process on models’ mechanical response remains unclear. This study investigates the influence of g-rising process on stress and deformation characteristics of these models. [Method] Centrifugal model tests for embankment loading were conducted in three loading conditions, i.e., layered rapid loading, layered slow loading, and non-layered slow loading. The settlement, rebound deformation, pile-soil stress distribution, and excess pore water pressure were investigated. The limitations of using g-rising method with different layering and loading rates were discussed. [Result] g-rising after shutdown for layered simulation causes an unloading-rebound-reloading cycle, leading to the subsoil exhibiting clear rebound and recompression characteristics. This results in a loading condition different from typical prototype conditions, increasing the complexity of deformation prediction and soil-pile interaction, and highlighting the effects of pore water pressure hysteresis and embankment slope. The composite foundation undergoes additional deformation during g-rising, resulting in larger settlement. The higher the g-rising speed, the greater the surface rebound upon unloading. The process of reload after shutdown causes the soil between piles to move upward relative to the piles, inducing the local tension in piles, and resulting in the underestimated pile-soil differential settlement and stress ratio. [Conclusion] Increasing the loading rate will reduce the deformation control capacity of composite foundation. Slowing the loading rate and converting the loading-after-shutdown to a continuous linear loading will benefit the deformation control. The simulation pattern of centrifugal model test for pile-supported embankment should fully consider the similarity between models’ stress history and actual prototype conditions.
  • Accuracy of vector sum method for slope sliding thrust
    LI Jiahang, GUO Mingwei
    2025, 42(12): 86-95,129. https://doi.org/10.3969/j.issn.1002-0268.2025.12.009
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    [Objective] The study evaluates the calculation accuracy of vector sum method for slope sliding thrust under the combined effect of dynamic variations in slide surface inclination and material parameters, thereby providing theoretical support for anti-slide engineering practices. [Method] A typical cambered slide surface slope case and a polygonal slide surface slope case with significant inter-slice inclination variation were selected. The finite element method was employed to obtain stress state within slopes, followed by calculation analysis with vector sum method for slope sliding thrust and comparison with the rigorous limit equilibrium Morgenstern-Price (M-P) method. A sensitivity analysis was performed on both strength and deformation parameters of soil mass to quantitatively evaluate their relative influence on computational outcomes. [Result] When the slide surface inclination variation reaches 45°, the error in safety factor between vector sum method and M-P method are less than 5%; while the maximum error of conventional transfer coefficient method exceeds 35%. The sliding thrust from transfer coefficient method shows significant correlation with the inclination variation, whereas vector sum method remains essentially unaffected by the inclination variation. Variations in soil internal friction angle, elastic modulus, and Poisson’s ratio minimally affect the calculation accuracy of vector sum method. [Conclusion] The vector sum method proves suitable for polygonal slide surface slopes with drastic inclination variations, providing reasonable and reliable sliding thrust and safety factor result. Vector sum method for slope sliding thrust would be a supplement for conventional transfer coefficient method, showing the promising applications in anti-slide engineering for slopes with excessive slip surface inclination variations.
  • Medium to long-term cumulative impact of fly ash road construction on environment
    ZHANG Dong, BAI Mingyue, WANG Jian, NI Dong, ZHANG Yutong
    2025, 42(12): 96-104. https://doi.org/10.3969/j.issn.1002-0268.2025.12.010
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    [Objective] This study aims to evaluate the medium to long-term cumulative impact of fly ash used as subgrade filler on the surrounding environment along expressways. Qinhuangdao-Laoting Expressway in Hebei Province was taken as a case study. [Method] The field investigation and sampling were carried out on soil, water, and vegetation along the expressway. The types and concentrations of main pollutants were analyzed, and the geoaccumulation index was applied to assess heavy metal pollution levels. [Result] The content of heavy metal elements in soil decreases with the increase of roadside distance. The contents of heavy metal elements in various places are all lower than that specified in the national standard, indicating that the risk of soil pollution around road caused by fly ash subgrade is relatively small. The geoaccumulation index of Cu at sampling points with different distances are all less than 0. The geoaccumulation indexes of Zn, Cr, Pb and other elements at sampling points with distances over 5 meters away are all less than 0, indicating no pollution. The pollutants and heavy metals detection result of water bodies on both sides of the expressway indicate that the water quality meets the standards of a first-class protected area for centralized drinking water sources. The average content of five heavy metal elements in ryegrass plants on both sides of sampling section, in descending order, is Pb, Cr, Cu, Cd, and Zn, all of which are below the limit values. The enrichment coefficients of Cd, Pb, and Cr fluctuate between 0.01 and 0.06, while the enrichment coefficients of Cu and Zn are both 0, indicating no pollution risk. [Conclusion] The cumulative pollution effect of fly ash filler on soil, water and vegetation on both sides of Qinhuangdao-Laoting Expressway is relatively light. The study result would provide theoretical support for the application of fly ash filler in expressway subgrade filling.
  • Water-saturated sandstone failure precursors under freeze-thaw cycles
    XIE Haotian, XU Ying, ZHENG Qiangqiang, ZHANG Qian
    2025, 42(12): 105-113. https://doi.org/10.3969/j.issn.1002-0268.2025.12.011
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    [Objective] Taking the sandstone collected from highway slope at Yulong copper mine in Tibet, this study investigated how freeze-thaw cycles affect the energy evolution and failure precursors of water-saturated sandstone. [Method] The sandstone samples were pretreated by using a freeze-thaw cycling test chamber. Static compression tests and real-time acoustic emission monitoring tests were conducted under different freeze-thaw cycles. The mechanical properties of freeze-thaw water-saturated sandstone and the acoustic emission characteristics during failure process were analyzed. The failure precursors of water-saturated sandstone in freeze-thaw conditions were illustrated based on the critical slowing down theory. [Result] The compressive strength, elastic modulus, and total strain energy of water-saturated sandstone decreased with freeze-thaw cycles increasing. Compared with those at unfrozen state, the compressive strength decreased by 34.38%, the elastic modulus decreased by 22.66%, and the total strain energy decreased by 29.77% after 120 cycles. With more freeze-thaw cycles, the failure mode of samples gradually changed from tensile-dominated tensile-shear failure to shear-dominated X-type shear failure. The b-value of acoustic emission, ring-down count variance and autocorrelation coefficient all served as failure precursory criteria. The predicted failure moment increased with freeze-thaw cycles. After 120 cycles, the failure moments predicted with b-value of acoustic emission, ring-down count variance and autocorrelation coefficient preceded the actual failure moment by 45.9 s, 68.4 s, and 73.2 s respectively. [Conclusion] The failure moments predicted with ring-down count variance and autocorrelation coefficient are both earlier than that predicted with b-value of acoustic emission.
  • Impact coefficient of steel-concrete composite beam bridge considering deck roughness degradation
    LI Ximei, ZHANG Jiancheng, MU Bohai, GUO Pengyi
    2025, 42(12): 114-121. https://doi.org/10.3969/j.issn.1002-0268.2025.12.012
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    [Objective] The steel-concrete composite beam bridge deck roughness is prone to gradually degradate under the combined action of vehicle loads and environmental factors, e.g., freeze-thaw and corrosion. This study analyzes the bridge impact coefficient varying with deck roughness degradation, and clarifies the variation rules of impact coefficient. It provides a scientific basis for traffic maintenance departments to effectively maintain and manage bridge decks. [Method] A steel-concrete composite continuous beam bridge with double I-beam was selected as the study object. The vehicle-bridge coupling vibration analysis was conducted in different deck roughness conditions to evaluate the influence of roughness variation on impact coefficient of bridge. First, a bridge deck roughness degradation model was proposed by combining bridge deck roughness coefficients and statistical data. Second, the vehicle-bridge coupling program was made by using Ansys software to analyze the influence of deck degradation on impact coefficient. Third, it considered the impact coefficient varying with the influence of deck roughness degradation. Finally, the correction factors, i.e., roughness and time, were introduced respectively on the basis of current specifications to modify the calculation formula of impact coefficient. [Result] The deck roughness continuously decreases with the increase of operation time, and the rate of decrease becomes greater and greater. There is a significant difference between impact coefficients and those calculated with current specifications when the deck roughness is at level C and level D. The impact coefficient increases exponentially with the increase of operation time. [Conclusion] The revised calculation formula could calculate the impact coefficients with different deck roughnesses, and predict the impact coefficients varying with operation time. It provides a reference for determining maintenance time of bridge deck pavement.
  • Design and application of prefabricated concrete bridge SS-level barrier structure
    BAO Gang, SHAO Chaoyi, YAN Shuming, ZENG Feng, MA Qing
    2025, 42(12): 122-129. https://doi.org/10.3969/j.issn.1002-0268.2025.12.013
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    [Objective] The prefabricated concrete bridge SS-level barrier structure was proposed based on the novel concept of embedded foundation design. The study validated barrier safety performances, and evaluated their safety and universality in various engineering conditions, providing comprehensive data support for the engineering promotion and application of barriers. [Method] The proposed method combined computer simulation and full-scale impact test with real vehicles. First, a reliability-verified simulated model was established based on SS-level impact conditions to simulate the process of vehicle impacting barrier. The safety performance of prefabricated barrier was evaluated. Considering the diversity of actual engineering conditions and ensuring the safety and universality of prefabricated concrete bridge barrier, the test conditions were set from less favorable perspectives, i.e., reducing maintenance duration of prefabricated concrete bridge barrier wall, reducing strength of bridge flange plate reinforcement, increasing installation adjustment gap reservation, and adopting unfavorable impact conditions. [Result] The protective capacity of prefabricated concrete bridge barriers reaches SS-level. Their safety evaluation indexes, i.e., containment performance, buffering performance and guiding performance, meet standard requirements. No serious structural damage occurred to the back block after impact test. Cracks only exist in the impact area. It is convenient for later maintenance in actual engineering applications. Simultaneously, the 2 cm adjusting gap between back block and barrier wall can adjust barrier longitudinal alignment. It makes the prefabricated barriers have convenient operation and overall aesthetics in practical engineering applications. [Conclusion] The safety performance of prefabricated concrete bridge SS-level barrier meets the standard requirements. It performs excellently in practicality, economy and aesthetics, achieving rapid assembly function, improving construction efficiency, shortening construction period, and saving construction cost; as well as ensuring operation safety of bridge section, optimizing project quality, and meeting overall construction needs of actual projects. It has extensive engineering application values.
  • Influence of ultra-close high-pressure chemical churning pile construction on existing pile foundations and adjacent soil
    WAN Qi, XIONG Lei, QIAN Nigui, SU Zhilei, DONG Peng
    2025, 42(12): 130-137,167. https://doi.org/10.3969/j.issn.1002-0268.2025.12.014
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    [Objective] The ultra-close high-pressure chemical churning pile construction in coastal soft soil areas causes disturbances to the existing pile foundation. This study investigated the disturbance evolution and multi-field coupling mechanism, providing technical support for ultra-close high-pressure chemical churning pile construction in soft soil areas. [Method] The in-situ full-scale test of pile foundation response to grouting construction was conducted based on a provincial road-expressway parallel section project in Guangdong Province. The deep horizontal displacement, earth pressure, and pore water pressure of pile foundation and adjacent soil were monitored simultaneously,defining the critical threshold value of shotcreting pressure and construction distance. [Result] The pile foundation horizontal displacement shows linear growth, and exponential decay with pile distance. The critical pressure for soil elastic-plastic deformation is 15 MPa; and the earth pressure at 1.0 m spacing reaches 110 kPa. It drops to 91 kPa due to soil plastic yielding when the grouting pressure is 20 MPa. Both earth pressure and pore water pressure exhibit near-field concentration and far-field attenuation. The pore water pressure at 1.0 m spacing reaches 68 kPa when the grouting pressure is 20 MPa. The pore water pressure attenuates by 72% when the spacing is 2.0 m; the pressure dissipates by 90% in 72 hours after construction. The pile-soil displacement follows Boussinesq model. The soil displacement is 10.1 times that of the pile. The pile foundation horizontal displacement increases 0.41 mm as the pore water pressure increases 10 kPa. The 10 m deep sand layer is a disturbance-sensitive layer, contributing over 75% to displacement. [Conclusion] The study revealed the coupling mechanism, i.e., high-pressure water jet, pore pressure accumulation, earth strength deterioration, and pile foundation displacement amplification. A hybrid control scheme was proposed, i.e., grouting pressure≤15 MPa, safe distance≥1.5 m, and sand layer pre-reinforcement. It provides the three-dimensional layer regulation basis, i.e., pressure-distance-soil, for ultra-close high-pressure chemical churning pile construction in soft soil areas.
  • Dynamic optimization method for stay cable force of long-span CFST arch bridge
    HOU Zhiyao, HU Qiang, QIN Zuojie, CHEN Qifeng, NING Jiejun
    2025, 42(12): 138-144. https://doi.org/10.3969/j.issn.1002-0268.2025.12.015
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    [Objective] This study proposed a novel optimization method for stay cable force. It addressed the limitation of traditional methods, which ignored the influence of structural behavior across different construction stages in segmental assembly of long-span CFST arch bridges. The goal was to ensure proper arch rib geometry throughout all construction phases. [Method] The theoretical analysis and numerical simulation were combined. First, the influence matrix method was used to explicitly express the relation between cable force and arch rib geometry at each construction stage. Then, the optimization objective function was formulated. The particle swarm optimization algorithm was applied to dynamically optimize cable forces stage by stage. Finally, the optimal stay cable force at each phase was yielded, ensuring the reasonable stress and geometry during entire construction process. [Result] The optimized cable forces show smooth variation throughout construction, with the uniformity exceeding 80%. Compared with the traditional single-tensioning method, the maximum geometric deviation of arch rib during segmental assembly is reduced by 157.6 mm. The peak stress on arch rib is also lower, decreasing by 68.8 MPa. The geometry deviations remain small and consistent across all stages, significantly better than those with the traditional single-tensioning method. Both assembly geometry and releasing cable geometry of arch ribs are well controlled after optimization. [Conclusion] The proposed method will ensure stable structural behavior and reasonable geometry throughout construction. It will effectively compute the optimal cable forces for cable-stayed buckling.
  • Cable saddle slip effect of deep-water extradosed bridge considering seismic hydrodynamic pressure
    LIN Xuechun, GU Yin, TANG Zuoping, WANG Zhen, YU Yi, LIN Daming
    2025, 42(12): 145-159. https://doi.org/10.3969/j.issn.1002-0268.2025.12.016
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    [Objective] This study investigates the cable saddle slip effect of deep-water extradosed bridge under seismic hydrodynamic pressure.It evaluates the influence of unbalanced cable force on anti-sliding performance of cable saddles; as well as provides a basis of seismic anti-sliding design for stay cables. [Method] The hydrodynamic additional mass of bearing platform was calculated by using radiation wave theory. The hydrodynamic additional mass of pile foundation was obtained with Morison equation. These additional masses were assigned as nodal masses at corresponding structural locations. A nonlinear finite element model of entire bridge was established considering seismic hydrodynamic pressure. The stay cable slip effect under seismic loading was examined through numerical analysis. The influence of varying water levels and seismic intensities on slip effect was investigated. [Result] The friction between saddle and stay cable alone is insufficient to resist the unbalanced cable forces induced by seismic excitation under the fortified earthquake (E2 level). Variations of water level have a pronounced, though complex, effect on sliding behavior. E2 level earthquakes may trigger sliding at different water levels. The inertial force amplification effect is the dominant factor due to the increased hydrodynamic additional mass, leading to a general trend of larger responses at higher water levels. Seismic intensity is the primary factor governing slip. The structure remains essentially stable under frequent earthquakes, whereas the significant slip occurs during rare earthquakes, which may jeopardize structural safety. When the earthquake intensity increases to 0.15g, the peak tension would reach 7 400 kN, and the peak unbalanced cable force close to 2 000 kN. The hydrodynamic coupling with structural vibration modes at specific water levels may further amplify the response, when the slip displacement increases nonlinearly with seismic intensity. [Conclusion] The stay cable slip should be taken as a critical verification item in view of seismic design for deep-water extradosed bridges. Reliance on friction alone for force transfer is inadequate. The effective anti-sliding devices or restraint measures should be adopted. These findings provide a useful reference for cable design and seismic performance evaluation of deep-water extradosed bridges.
  • Cushioning effect of steel-polyurethane foam core device against ship collision
    XUE Xiaoling, YU Guojun, DU Chengbin, MENG Zhuang, YAN Jie
    2025, 42(12): 160-167. https://doi.org/10.3969/j.issn.1002-0268.2025.12.017
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    [Objective] This study investigated the cushioning effect of steel-polyurethane foam core device against ship collision. The second Nanjing Yangtze River Bridge, i.e.,North Branch Bridge, was taken as the case study. [Method] A high-precision 3D finite element model was established with LS-DYNA software. The model simulated ship collisions with the anti-collision device by using explicit dynamic calculations. Several indicators, e.g., collision depth, peak force and average collision force, were analyzed to comprehensively evaluate the cushioning effect. The influences of steel plate thickness and polyurethane foam density on cushioning effect were studied. [Result] The mechanical properties of anti-collision device show distinct regularity. The overall stiffness is inversely related to the maximum collision depth. The peak force and average collision force are positively correlated. The device energy is dissipated through the steel plate and polyurethane foam in synergy. The maximum collision depth is reduced by 23.36% when increasing steel plate thickness from 8 mm to 10 mm. The collision depth is reduced by 35.37% when increasing polyurethane foam density from 40 kg/m3 to 50 kg/m3. These results indicate that the material parameters significantly influence cushioning effect. Increasing both steel plate thickness and polyurethane foam density improves the cushioning effect of device. [Conclusion] The best design is 50 kg/m3 polyurethane foam with 10 mm steel plate. This design will achieve the collision reduction rate of 21.03%, meeting regulatory standards and cost-effective.
  • Incremental launching closure method optimization for multi-extradosed bridge based on multi-objective control strategy
    ZHAO Xin, TIAN Lianmin, YING Shiming, FU Yingzi, ZHANG Zhendong, ZHAO Yue
    2025, 42(12): 168-176. https://doi.org/10.3969/j.issn.1002-0268.2025.12.018
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    [Objective] Unreasonable incremental launching sequences and incremental launching parameters will cause the excessive reverse displacement and adverse internal forces during incremental launching closure of long-span multi-extradosed bridge. This study proposed the incremental launching closure optimization method for multi-extradosed bridge,providing reliable technical support for the scientific selection of closure schemes and the optimization of key parameters for similar bridges. [Method] The study considered the characteristics of multi-extradosed structures, i.e., single indicator corresponding to multiple component responses; took the overall response of complex structure as the control objective; introduced the empirical entropy weight method to establish a multi-objective control evaluation model based on hierarchical weighting. A bridge finite element model was established based on Xilamulun river bridge with six pylons and seven spans. The structural responses were simulated and analyzed with different closure sequences and incremental launching parameters. The multi-component response value of each key indicator was calculated. Finally, the comprehensive optimization was conducted based on the evaluation model. [Result] The closure sequence has a little influence on the indicators of multi-extradosed bridge at completed bridge state, while the incremental launching force significantly affects the pylon-beam displacement, pier top displacement, and pier bottom stress during the bridge operation. The incremental launching force optimization would effectively improve the structural response and reduce the adverse effects caused by internal forces and deformations. [Conclusion] The optimal incremental launching force, determined with the multi-objective evaluation method based on overall structural response, differs from that obtained with the traditional peak value method. The proposed hierarchical weighting multi-objective control evaluation model would effectively adapt to the complex characteristic of multi-extradosed structures. The study result provides the important reference for ensuring the completed bridge alignment and structural safety of similar bridges.
  • Wear life evaluation method for sling pin bushings
    WU Shanggang, ZHANG Wei, SUN Yuwei
    2025, 42(12): 177-184. https://doi.org/10.3969/j.issn.1002-0268.2025.12.019
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    [Objective] This study aims to efficiently evaluate sling pin bushing fatigue wear performance, and analyze the influence of different bushing materials on fatigue wear life of bushing; so that the wear state of pin bushing could be evaluated through a simple sling inclination test, supporting the theoretical support for preventive maintenance strategy for suspension bridges. [Method] Two fatigue life evaluation methods were proposed based on cumulative damage theory and reliability theory. The analysis incorporated mechanical parameters of pin bushings from Jiangyin bridge, long-term sling inclination monitoring data, and comparative wear tests on four bushing materials, i.e., DU, tin bronze, aluminum bronze, and aluminum brass. [Result] The cumulative wear of pin bushing is found to be primarily induced by high-frequency, low-amplitude oscillatory motion at sling end. The number of load cycles leading to bushing failure follows a log-normal distribution. The tin bronze bushings exhibit the longest fatigue life among four materials. The tin bronze bushing has longer fatigue life than others. When using tin bronze, the estimated service life is 13.37 years based on the cumulative damage method, and 11.68 years based on the reliability-based method. [Conclusion] Both evaluation methods would effectively evaluate bushing fatigue life through sling inclination monitoring parameters. The reliability-based method yields a more conservative fatigue life, showing a reduction of 11.11%-13.64% compared with the cumulative damage method. With its capability for dynamic adjustment of target reliability index, the reliability-based method demonstrates more enhanced engineering applicability.
  • Disaster prevention and control technology for tunnel crossing water-rich and weak fractured surrounding rock
    XU Chao, LUO Hua
    2025, 42(12): 185-196,209. https://doi.org/10.3969/j.issn.1002-0268.2025.12.020
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    [Objective] In tunnels with water-rich and weak fractured surrounding rock, the compound disasters often occur, e.g., mud surge, water gush, working face instability, and external high water pressure. It is therefore urgent to propose an integrated set of mitigation measures. [Method] Relying on Daliangshan tunnel, this study adopted seepage theory and geotechnical deformation control analysis, combining with tunnel drainage and waterproofing principles. It analyzed the mechanisms of tunnel gushing water, working face instability, and external water pressure on lining. Based on analysis, it developed the mitigation schemes and compared different combined schemes through numerical simulations. Finally, the proposed scheme was applied and evaluated in Daliangshan tunnel. [Result] When the radial grouting is provided, the scheme, combining advanced pipe-roof support and advanced small pipe support with two-step method, can effectively control longitudinal displacement at working face and crown settlement. Compared with schemes of two-step method or two-step method with reserved core soil combining with advanced small pipes, it also reduces the external water pressure on lining by 16%. The in-situ application shows that the maximum external water pressure on lining is 95.61 kPa, which has a limited influence on structural safety. The maximum stress on primary support steel frame is 49.47 MPa, which is far below the yield strength of steel. The safety factor of secondary lining is much greater than that required by specification. [Conclusion] Strengthening pre-support, compared with reserving core soil, provides more effective control on working face collapse and gushing water risks for water-rich and weak fractured surrounding rock.
  • Color transition section length calculation for colored pavement in tunnels based on luminance requirement
    WANG Jiazhu
    2025, 42(12): 197-209. https://doi.org/10.3969/j.issn.1002-0268.2025.12.021
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    [Objective] The study optimized settings of luminous environment and colored pavement in tunnels to improve the driving safety and comfort. The color transition section length calculation method for colored pavement in tunnels was put forward based on luminance requirement. [Method] First, considering drivers’ physiological and psychological characteristics, the luminance requirement in tunnels was analyzed. Several typical tunnels in Fujian Province were taken as the study cases. The model of luminance requirement in tunnels was proposed through the specification-based tunnel luminance requirement calculation and regression fitting analysis. The model satisfied the demand for driving comfort. Second, in combination with distribution of colored segments of pavement, the location ranges of end points of color transition sections were studied. Then, in accordance with the quartiles of luminance requirements, the end points of pavement color transition section were defined. The model of color transition section length of tunnel pavements based on luminance requirement was set up. Meanwhile, the color transition section length calculation process was provided. Finally, taking Tianqiling tunnel in Fujian Province for example, the color transition section length of tunnel pavement was calculated. The schemes before and after optimization on color transition section length were compared and evaluated by using DIALux software and eye trackers. [Result] The optimized scheme would have significantly decreased uncomfortable time ratio based on pupil area change rate, compared with the original design scheme, i.e., without color transition sections. The uncomfortable time ratio decreased by an average of 29.16%. The total uniformity of pavement luminance increased to a certain extent by an average of 14.58%. [Conclusion] The color transition section length calculation method for colored pavement in tunnels based on luminance requirement is beneficial for upgrading the driving comfort and luminance uniformity. It helps perfect the theory for setting colored pavements in tunnels and increase their applicability.
  • Quantitative analysis on stability of surrounding rock reinforced with vacuum water pumping through fault fracture zones
    LI Lei, XIANG Qian, HUANG Chao
    2025, 42(12): 210-222. https://doi.org/10.3969/j.issn.1002-0268.2025.12.022
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    [Objective] The working face instability often occurs in tunnels through fault fracture zones in water-rich areas, while existing reinforcement techniques lack quantitative basis. This study clarified the regulatory mechanism of vacuum water pumping reinforcement on surrounding rock stability, thereby proposing a quantitative reinforcement scheme directly guiding construction. [Method] The muddy siltstone (Class V), from Jiawu tunnel on Yichang-Badong expressway in Hubei Province, was studied. The shear strength test and constant head permeability test were conducted to determine the correlation patterns between rock mass moisture content and shear parameters, as well as dry density and permeability coefficient. A numerical model was constructed based on the seepage-stress coupling theory to simulate surrounding rock responses with different vacuum levels, fault gouge dip angles, and nonlinear coefficients. The dynamic changes in core mechanical parameters were analyzed in the reinforced area. [Result] The surrounding rock stability control with vacuum water pumping reinforcement had obvious regional limitations. As the absolute value of vacuum degree increased, the pore ratio of surrounding rock decreased from the initial 0.287 to 0.267, with a maximum decrease of 7.1%. The negative pressure zone continued to expand, and the stable pumping time had been extended from 1.5 hours to 1 100 hours. The maximum changes in permeability coefficient, elastic modulus, and internal friction angle were 5.9%, 5.2%, and 11.2% respectively, while the change in cohesion was relatively small (only 0.6%). [Conclusion] Vacuum water pumping would enhance the short-term stability of muddy siltstone surrounding rock by optimizing pore structure; however, it could not alter the rock mass strength grade. It is necessary to combine auxiliary construction methods to achieve the improvement of surrounding rock grade.