20 January 2023, Volume 36 Issue 1
    

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    Road Engineering
  • Research Advances of Aggregate Characteristics, Interface Effect, and Migration Behaviors of Multi-level Aggregate-asphalt System
    LI Pei-long, SU Jin-fei, SUN Sheng-fei, WANG Xiao, MA Yun-fei
    China Journal of Highway and Transport. 2023, 36(1): 1-15. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    An asphalt mixture is a multi-level and multi-phase granular material, in which the complicated aggregate characteristics, interface effect, and migration behaviors determine the segregation properties, compaction quality, and mechanical responses. Elucidating the mesoscopic mechanism of asphalt mixtures and providing a theoretical basis for the design optimization, construction control, and performance analysis of asphalt mixtures helps improve the durability of asphalt pavement. This paper reviews the outcomes of existing research on aggregate-asphalt systems. Asphalt mixtures used in paving, compaction, and service processes are regarded as different states of aggregate-asphalt systems with different degrees of freedom of migration. First, focusing on the aggregate characteristics, the effects of geometric morphologies and size of the aggregates on the performance of the asphalt mixture are analyzed; based on this analysis, the method for the calculation of composite geometric characteristics is described. Subsequently, considering the loose aggregate-asphalt system, the mesoscopic properties are described, including the contact-friction properties of the particle system and the interface interaction of the aggregate-asphalt system. Subsequently, the evaluation methods used for the segregation of asphalt mixture are summarized; the effect of particle migration on the segregation tendency of asphalt mixture is analyzed, and the forming mechanism of mixture segregation is discussed. Considering the compaction process of asphalt mixtures, the dynamic compaction properties of asphalt mixtures and the migration behaviors of particles are discussed; the influence of the geometric characteristics and the interface effect on the particle migration are analyzed, and the compaction process of the asphalt mixture is discussed based on the migration behaviors. Considering the compacted asphalt mixture, the spatial migration behavior of the aggregate-asphalt system is summarized, and the influence of the micromigration behavior on the mechanical strength properties of the asphalt mixture at the mesoscopic level is analyzed. Finally, the asphalt mixtures used in the transportation and paving, compaction, and service processes are defined as aggregate-asphalt systems with large-degree-of-freedom, small-degree-of-freedom, and micro-degree-of-freedom migration properties, respectively. The development tendency of interface behaviors and the migration dynamic properties of aggregate-asphalt systems are summarized, and prospects for further research are discussed. This review provides a reference for the basic theoretical research on the microscopic and mesoscopic characterization and mechanical response of asphalt mixtures, which will help improve mixture design, construction techniques, and maintenance quality.
  • Rheological Properties and Modified Mechanism of Polyurethane Solid-solid Phase Change Materials Modified Asphalt
    LIU Tao, GUO Nai-sheng, JIN Xin, HOU Yi-lie, YOU Zhan-ping
    China Journal of Highway and Transport. 2023, 36(1): 16-26. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.002
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    To evaluate the potential of polyurethane solid-solid phase change materials (PUSSPCMs) as asphalt modifiers, the influence of PUSSPCMs soft segments on the rheological properties and mechanism of asphalt was investigated. Therefore, PUSSPCMs with different soft-segment mass fractions (P70, P75, P80, P85, and P90) and the corresponding PUSSPCMs modified asphalt were prepared as testing materials in this study. Temperature regulating properties, dynamic shear rheology (DSR), and bending beam rheology (BBR) tests were used to investigate the temperature regulation and rheological properties of PUSSPCMs modified asphalt, and the modified mechanism was analyzed by differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and atomic force microscopy (AFM). The results show that PUSSPCMs modified asphalt exhibits better temperature-regulating properties than base asphalt, as well as greater deformation resistance and high-temperature performance, while low-temperature performance is lower. The temperature regulating properties and low-temperature performance of PUSSPCMs modified asphalt are greatly enhanced as the soft segment mass fraction increases, while the deformation resistance and high-temperature performance are correspondingly reduced. P90 asphalt has the best temperature-regulating properties and low-temperature performance, whereas P70 asphalt has the highest deformation resistance and high-temperature performance. PUSSPCMs have excellent heat storage-release properties, and P90 has a greater enthalpy and a lower initial temperature than P70. Furthermore, the enthalpy of PUSSPCMs is closely linked to the temperature-regulating properties of PUSSPCMs modified asphalt. In addition, there is no new functional group between the PUSSPCMs and asphalt, which means that it is a physical modification. As the soft segment mass fraction of PUSSPCMs increases, the "bee-like structure" of the asphalt expands, while the difference between the peripheral phase state and Young's modulus decreases. These are inextricably related to the high- and low-temperature performances of PUSSPCMs modified asphalt.
  • Calculation Method for Limit Passive Frictional Resistance Induced by Convex Nodes of Hyperstatic Geogrid
    CUI Xin-zhuang, WANG Yi-lin, JIANG Peng, JIN Qing, CHEN Lu
    China Journal of Highway and Transport. 2023, 36(1): 27-36. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.003
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    Geosynthetic-soil interaction is a critical factor influencing the bearing capacity and stability of geosynthetic-reinforced soil structures. Several studies have shown that hyperstatic geosynthetics, designed with additional structures based on traditional geosynthetics, effectively improve the strength of geosynthetic-soil interfaces. However, the improvement mechanism of additional structures of hyperstatic geosynthetics still requires further investigation. In this study, high-resistant hyperstatic geogrids (HRHGs) designed with convex nodes were employed. In the limit equilibrium state, a logarithmic spiral-curved-surface failure mechanism was assumed by incorporating the lateral interfacial shear strength of HRHG nodes. In addition, a mechanical analytical model of the HRHG nodes was established to improve the interfacial strength of the reinforced soil. The model simulated the passive resistance of HRHG nodes in limit geogrid-soil interaction, and a method for calculating the ultimate passive resistance of HRHG nodes was developed. Based on a self-developed large-scale direct shear apparatus, direct shear tests on the HRHG and traditional bidirectional geogrids were performed with low-liquid-limit silt under different normal pressures (30, 50, and 80 kPa). The test results show that the convex nodes of HRHG increase the apparent cohesion and friction angle of geogrid-silt interfaces by 35.6% and 14.3%, respectively. The comparison between the test and calculation results validates the proposed calculation method for determining the ultimate passive resistance of HRHG nodes. Furthermore, the calculation method was revised based on the test results, providing a reference for the design and practical application of HRHGs.
  • Improved Duncan-Chang Model Based on Mechanical Properties of Coarse-grained Soil Filling of Embankment
    HE Zhong-ming, LIU Zheng-fu, XIANG Da
    China Journal of Highway and Transport. 2023, 36(1): 37-46. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.004
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    To study the influence of dynamics and moisture content on the mechanical properties of embankment filling with coarse-grained soil, samples of coarse-grained soil under different moisture contents w were prepared. Dynamic stress with different frequencies f was applied to the samples, and then static triaxial compression tests were performed. The σ0-ε1 curves of the different samples were analyzed. According to the Janbu formula, the correlation between the dynamic deviator stress σd, moisture content w, load frequency f, and parameters n and K were explored. The fitting formulas for the initial deformation modulus Ei, ultimate deviator stress (σ0)ult, and controlled variables were established. An improved Duncan-Chang model was proposed for coarse-grained soil considering the influence of the dynamics and moisture content. Finally, verification tests were conducted to analyze the effectiveness of the revised model. The results show that the deformation of the samples changes from elastic to plastic when ε1>0.5%. Under different controlled factors, the σ0-ε1 curves of the samples change significantly in the range of 0.5%<ε1<2.0%. The tangent deformation modulus Et also changes considerably within this range; the reduction rate reaches 58%-76%. When ε1>2%, the change in Et gradually decelerates and stabilizes. The samples exhibit strain-hardening characteristics during loading. As the moisture content, dynamic deviator stress, and load frequency increase, the deviator stress decreases when it reaches the same axial strain in the static triaxial tests. The initial elastic modulus Ei of the coarse-grained soil was related to the third principal stress σ3. A linear relationship exists between lg(Ei/Pa) and lg(σ3/Pa). The parameter n in the Janbu formula is not sensitive to controlled factors. In these tests, the value of n is stable at 0.78-0.80. The relationship between σd, w, f, and parameter K is nonlinear. Parameter K decreases with an increase in σd and w, while f shows an opposite trend. The power function can be used to establish the relationship between Et and controlled factors, the relationship between (σ0)ult and controlled factors is the same. Validation tests show that the improved constitutive model in this study can effectively predict the σ0-ε1 curve of the coarse-grained soil filling of embankments with different σd, w, and f.
  • Investigation of Shear Behavior of Calcareous Sand in Consolidated and Drained Triaxial Tests
    LIU Meng-cheng, CHEN Mao-lin, WANG Juan
    China Journal of Highway and Transport. 2023, 36(1): 47-57. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.005
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    To provide references for design and construction of infrastructures in the hydraulic fill foundation of calcareous sand in the coral reef of South China Sea, a series of triaxial tests were carried out to investigate the consolidated and drained shear behavior of calcareous sand. The stress-strain-volume change and stress path behavior of calcareous sand were quantitatively analyzed, and the normalized formulations and its parameters of the shear strength, internal friction angle and porous ratio at various characteristic states were put forward by means of the nonlinear fitting of test data, and the further quantitative analyses were made for their characteristics of nonlinear evolution. The research findings indicate that:① calcareous sand exhibits strain softening and volume dilation when the confining pressure is less than 300 kPa; the deviatoric stress at the characteristic states increases with the confining pressure and relative density, and volume strain increases with the confining pressure or it decreases with the relative density; the stress path upon shearing in consolidated and drained triaxial tests are a series of parallel straight lines and its length is also larger when confining pressure is higher. ② the shear strength or internal frictional angle at the characteristic states is well normalized in various relative density, and shear strength at peak state (PS) is over that at phase transformation state (PTS), and meanwhile shear strength at PTS is over that at critical state (CS); it is merely a power or logarithm function of normalized mean principal stress, and the effect of relative density on the excessive internal frictional angle decays with the confining pressure and finally disappears. ③ in the compression plane the characteristic state porous ratio decreases with the normalized mean principal stress, and the critical state void ratio is well normalized in various relative density; the characteristic state porous ratio can be characterized with a negative exponential function, the upper and lower limit of which are in agreement with the actual limits of the characteristic state porous ratio.
  • Fluid-solid Coupling Model Considering Solid-liquid Two-phase Interaction Characteristics
    LU Yu-dong, GUO Jin-qi, CHENG Da-wei, MAO Xing-long
    China Journal of Highway and Transport. 2023, 36(1): 58-69. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.006
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    This study focuses on the construction of fluid-solid coupling model considering solid-liquid two-phase interaction characteristics to study the deformation and settlement of road buildings/structures in road engineering caused by hydro-mechanical interactions in rock soil. First, the solid phase physical property parametric equation(Young's modulus, bulk modulus, and ultimate deviatoric stress) with moisture content as the parameter and liquid phase physical property parametric equation(saturated moisture content, residual moisture content, and parameters of the Gardner model) with the void ratio as the parameter are constructed. Second, the solid phase constitutive equation (Duncan-Zhang model) and liquid phase constitutive equation (Gardner model) are established considering the influence of the solid-liquid two-phase interaction, and the newly constructed constitutive equation and solid-liquid two-phase governing equation are combined to construct the fluid-solid coupling model that considers solid-liquid two-phase interaction characteristics. With unsaturated loess as the research object, using numerical simulation software to consider the influence of the solid-liquid two-phase interaction and a numerical model on the unsaturated soil, the influence mechanism of solid-liquid two-phase interaction characteristics on fluid-solid coupled in unsaturated soils was explored. The specific research results are as follows:with increasing moisture content, the solid phase physical property parameter tended to decrease; soil strength decreases as moisture content increases, and soil stress decreases when the strain is unchanged. As moisture content increases, the soil load decreases under the same deformation conditions. As the void ratio increases, the saturated moisture content increases linearly, and the residual moisture content decreases linearly. Parameter β in the Gardner model decreases exponentially, and the effective saturation in the soil increases accordingly. An increase in the void ratio also leads to the saturated hydraulic conductivity decreasing and unsaturated relative permeability coefficient increasing. Under the same loading conditions, compared with the fluid-solid coupling model without considering mutual effects, the model with mutual effects can simulate larger soil deformations, smaller moisture content, and pressure head.
  • Experimental Study on Mechanical Properties of Rubber-sand Cementing Materials Under Freeze-thaw Cycles
    YIN Ping-bao, LUO Pei-ting, YANG Zhao-hui, ZENG Ling, YU Wei
    China Journal of Highway and Transport. 2023, 36(1): 70-79. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.007
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    In seasonally frozen soil areas, freezing and thawing change the strength of the soil around the pile and induce diseases of pile foundations. Therefore, it is necessary to develop a new material which can replace the soil around the pile and to determine the influence mechanism of temperature and freeze-thaw cycles on the mechanical properties. Rubber particles, sands, and polyurethane glues were proportioned to prepare triaxial testing samples. Unconsolidated and undrained static triaxial tests were performed to obtain the stress-strain curves of the samples under different test conditions. Subsequently, the fitting relationships between the tangent modulus, tangent Poisson's ratio, and axial and radial strains were established by nonlinear fitting and regression analysis. The effects of freeze-thaw cycles, test temperatures, and confining pressures on rubber-sand cementing materials were analyzed. The results show that the stress-strain curves of rubber-sand cementing material samples have no peak point, so the material is a typical strain hardening material. The tangent modulus of rubber-sand cementing materials is between 2.0 MPa and 9.0 MPa. The temperature has a significant influence on the failure strength and tangent modulus of the sample, while the number of freeze-thaw cycles and low confining pressures have relatively less influence. The tangent Poisson's ratio of rubber-sand cementing materials is approximately 0.50-0.75, and increases with an increase in radial strain. However, the tangent Poisson's ratio is not significantly affected by the number of freeze-thaw cycles, temperatures, and low confining pressures. Rubber-sand cementing materials are expected to provide support for freezing-thawing and for the prevention of frost heaving in pile foundations in seasonally frozen soil areas.
    • Bridge Engineering
  • Research Advances of Across-fault Ground Motions and Their Effects on Bridge Structures
    ZONG Zhou-hong, LIN Yuan-zheng, LIN Jin, LI Ya-le
    China Journal of Highway and Transport. 2023, 36(1): 80-96. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.008
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    Compared to scenarios under conventional ground motions, bridge structures subjected to across-fault ground motions have more complicated dynamic responses, larger seismic demands, and more severe seismic damage. With the development of super-infrastructure, such as the Sichuan-Tibet railway, an increasing number of bridges are facing the hazard of crossing potential faults; therefore, relevant studies are urgently needed. Based on the seismic damage of fault-crossing bridges, this paper first demonstrates the basic characteristics of near- and across-fault ground motions and introduces the relevant simulation methods. Then, studies on the analysis theory, numerical simulation, and model tests of fault-crossing bridges are reviewed, and coping strategies against the fault-crossing effect are summarized. The results show that the current simulation methods of across-fault ground motions are generally reasonable and feasible, but certain application conditions exist and improvements are needed; the studies on fault-crossing bridges mainly focus on middle- and small-span girder bridges, and the seismic responses and damage modes of bridges are affected by multiple factors, including fault type, fault-crossing location, fault-crossing angle and permanent displacement. The seismic isolation technique and the anti-collapse displacement restriction measurements for fault-crossing bridges have achieved preliminary improvements. Finally, development orientations for future studies on fault-crossing bridges are proposed in this study. In particular, more accurate and efficient simulation techniques for across-fault ground motions need to be developed; shake table array tests and numerical studies on long-span fault-crossing bridges need to be conducted, the difficulties with the experimental technique of shake table array tests for fault-crossing bridges need to be solved, the influences of ground motion parameters on different types of fault-crossing bridges need to be explicitly pointed out, and seismic isolation, anti-collapse, and resilient techniques should be further developed and experimentally validated. This study can provide a reference for the simulation of across-fault ground motions and the analysis and design of fault-crossing bridges.
  • Research Advances on Multiscale Uncertainty Quantification for Fiber Reinforced Polymer Composite Structures
    ZHOU Xiao-yi, QIAN Sheng-yu, WANG Neng-wei, XIONG Wen, WANG Xin, CAI Chun-sheng
    China Journal of Highway and Transport. 2023, 36(1): 97-113. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.009
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    The application of fiber-reinforced polymer (FRP) composites in bridge structures has garnered an increasing interest. However, the complicated manufacturing processes and complexity of microstructures of FRP composite structures lead to larger variations in the performance of FRP composites compared with those of structures made of conventional materials. In addition, reliability and safety of FRP composite structures are difficult to determine. This study provides a comprehensive review of the sources of uncertainty, probabilistic prediction methods of material mechanical properties, and structural reliability to explore the state-of-the-art uncertainty quantification for FRP composite structures and research trends. In terms of the sources of uncertainty, starting from the classification of composite material manufacturing defects, causes of typical manufacturing defects, their influences on the mechanical properties of composite materials, and caused uncertainties are elaborated. In terms of the probabilistic prediction methods of material mechanical properties, the application scope of the perturbation-based stochastic finite element and spectral stochastic finite element methods for probabilistic homogenization are reviewed. Additionally, the application of these methods to determine the influences of microscope uncertainties on the macroscale mechanical properties is discussed. In terms of the structural reliability analysis, the existing methods and research results of the static, dynamic, buckling stability, and reliability analyses of FRP composite structures are reviewed. Studies have demonstrated that significant geometric multiscale levels and complex manufacturing processes of FRP composite materials inevitably produce various defects, and cause mechanical performance degradation and dispersion. The principal tools to analyze multiscale uncertainties include implementing experiments, micromechanical models, and homogenization methods, combined with stochastic finite element methods, etc., to propagate uncertainties from constituent materials and plylevel properties to structural responses. Experiments can only measure composite materials with specific component materials, whereas theoretical models are typically stablished under certain assumptions. Neither existing experimental nor theoretical methods can comprehensively describe uncertainties in the mechanical properties and structural responses induced by realistic manufacturing defects. Therefore, the development of uncertainty quantification methods based on the computational homogenization method is a future direction for the multiscale uncertainty analysis of FRP structures.
  • Experimental Study on Extreme Wave Loads Acting on T-Girder Type Superstructure of Coastal Bridges
    FANG Qing-he, LI Su-chao, GUO An-xin, LI Hui
    China Journal of Highway and Transport. 2023, 36(1): 114-123. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.010
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    Extreme waves generated by hurricanes, as one of the most critical disasters that threatens the safety of bridge structures, have damaged many low-lying coastal bridges along the Gulf of Mexico. Thus, exploring the mechanism of typhoon waves acting on bridge superstructures is significantly important to develop a method to calculate wave forces. Periodic focused waves were employed as incident waves to investigate the effect of wave forces on bridge superstructures considering the spectral characteristics of extreme typhoon waves. A set of model tests with different maximum amplitudes, peak frequencies, and clearances were conducted. The specimen was designed following the Froude criterion on a 1:25 scale using a prototype of a T-girder bridge. The horizontal and vertical forces acting on the T-girder bridge with different clearances were measured in a wave flume. Consequently, periodic focused waves, with an appropriate period, are adequate to avoid the pollution of the incident wave caused by re-reflection, which guarantees the credibility of the test results. The low-frequency quasi-static and high-frequency slamming forces are the two components of wave forces. The peak value of the slamming force typically appears in the initial stage of wave water contact with the bridge deck. In general, the force of a wave increases with its amplitude. However, an apparent non-monotonic trend can be observed between the force and amplitude of a wave; thus, wave forces acting on the T-girder bridge first decrease and subsequently increase with changes in clearance. At a peak frequency of 0.4 Hz, a large-amplitude focused wave generates maximum wave forces on the bridge with a clearance in the range of 2.0-3.0 cm. A simple method was developed to calculate wave forces based on the experimental data, thereby providing a reference for bridge design.
  • Influence of the Fairing Combination Measure Shape on the Vortex-induced Vibration Performance of a Cable-stayed Bridge with Π-shaped Composite Girder
    HUANG Lin, DONG Jia-hui, CHEN Chen, WANG Qi, LIAO Hai-li
    China Journal of Highway and Transport. 2023, 36(1): 124-134. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.011
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    Vortex-induced vibration (VIV) of a long-span cable-stayed bridge with a Π-shaped steel-concrete composite girder often occurs at high wind speeds. To suppress the girder VIV, the effects of different measures on the VIV under the most unfavorable condition of -5° wind attack angle were studied using a 1:50 scale sectional model wind tunnel test. First, the effects of some regular aerodynamic measures, such as baffles, aprons, lower central stabilizers, wind barriers, and fairings on the VIV performance of the girder were studied. The test results showed that only the lower central stabilizer could reduce the vertical and torsional VIV amplitudes of the girder by more than 50% at a damping ratio of 0.65%. Based on this, the following studies on combined aerodynamic measures centered on the lower central stabilizer were conducted, and it was found that the combined aerodynamic measures of the fairing and the lower central stabilizer can simultaneously reduce the vertical and torsional VIV amplitudes of the girder by more than 75%. On this basis, the height effects of the fairing vertical plate and the lower central stabilizer on the VIV damping performance of the combined measures were studied. It was found that within a certain height range, increasing the height of the fairing vertical plate and the lower central stabilizer can improve the VIV damping performance of the combined measure, and the aerodynamic shape of the combined aerodynamic measures was optimized accordingly. The optimized measures can eliminate the VIV of the Π-shaped composite beam under different wind attack angles (0.65% damping ratio). Finally, the VIV suppression mechanism of the aerodynamic measure was studied using computational fluid dynamics. The calculation results showed that the combination of fairing and lower central stabilizers can simultaneously reduce the vortex size on the upper and lower surfaces of the girder and effectively reduce the unsteady aerodynamic force on the girder, thereby suppressing the VIV of the girder. The reduction in the height of the fairing vertical stabilizer and lower central stabilizer can cause an increase in the size of the vortex of the cross-section shedding and reduce the VIV damping performance of the combined measures.
  • Temperature Gradient Action of Steel-concrete Composite Girder Bridge: Regional Difference and Isoline Map
    LIU Jiang, LIU Yong-jian, MA Zhi-yuan, LYU Yi
    China Journal of Highway and Transport. 2023, 36(1): 135-149. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.012
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    To study the regional differences in temperature gradient actions of composite girders and based on long-term historical meteorological data collected from 839 weather stations in China, the Bahel model of 91 radiation weather stations (with solar radiation data) was established, and the daily total solar radiation data of 748 regular weather stations (without solar radiation data) for 23 years were supplemented further. By using these meteorological data, a "layer-by-layer drawing method" was put forward for the isoline map of the temperature action representative value. In this method, the temperature action samples of 91 radiation weather stations and 748 regular weather stations were first obtained by long-term calculations using the finite-element method and meteorological correlated empirical formula, respectively. Then, the temperature action representative values of each weather station were obtained based on the superthreshold model of the generalized Pareto distribution. Finally, the isoline map of each temperature action was drawn using spatial interpolation. Using the above method, temperature difference isoline maps were drawn for Heating Pattern 1, Heating Pattern 2, and the cooling pattern of composite girder bridges. The research results show that the Bahel model has good applicability in China and can be used for accurate prediction of and to supplement solar radiation data. There are significant regional differences in the temperature difference of composite girder bridges in China, the maximum value of which can reach 27.89℃. If a certain value is selected in a large area, this regional difference will be underestimated. The concept of the layer-by-layer drawing method is clear and easy to implement, and it is demonstrated to be an effective method for drawing a temperature difference isoline map. An isoline map with a representative value of temperature difference in a 50-year return period can be used to provide an accurate and nationwide value for the temperature gradient of composite girder bridges. Compared with the current specification, the temperature difference data provided can meet the basic requirements of the limit state design method, which is of great value for the refined design of composite girder bridges in China, and to supplement the specification system.
    • Tunnel Engineering
  • Study on Law of Water Migration in Surrounding Rock During Construction of Water-rich Loess Tunnel
    LAI Hong-peng, TAN Zhi-peng, SUN Yu-kun, HUANG Peng-zhi
    China Journal of Highway and Transport. 2023, 36(1): 150-161. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.013
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    To provide guidance for the construction of water-rich loess tunnel, and relying on the Shanggecun Tunnel of Yinxi High-speed Railway, the basic law of water migration in a tunnel covered with soft plastic loess layer on the typical section was obtained through field monitoring. The relationship between the porosity ratio and permeability coefficient of the surrounding rock, the water content, and strength of the surrounding rock was established through laboratory tests. The relationship formula was programmed by FISH language in FLAC3D, and the dynamic permeability coefficient was assigned to the soil unit, which realized the simulation of tunnel excavation under the action of fluid-solid coupling. Numerical simulation results were verified by field monitoring data, and the results show that the simulation is reliable. Finally, based on the simulation results of 16 working conditions, the law of moisture migration in the surrounding rock during tunnel excavation and unloading at different distances from the overlying soft plastic loess layer to the tunnel vault is revealed. The results lead to the following conclusions. ① Under disturbance of excavation, the water in the soft plastic loess layer overlying the tunnel migrates from the bottom of the loess layer to the palm surface, and finally accumulates at the bottom of the tunnel. The water migration starts before the excavation of the palm surface and ends after the inverted arch is closed. ② When the distance between the vault and bottom of the soft plastic loess layer is 0 m ≤ h ≤ 4 m, a change in the position and pressure heads causes water migration around the tunnel. The water migration speed is high and the migration volume is large. Before the tunnel invert is closed, water easily invades the excavation surface. When 5 m ≤ h ≤ 8 m, a change in the position head causes water migration around the tunnel. The water migration speed is low and the migration volume is small. When h>8 m, there is no evident water migration during the construction of the tunnel. ③ When 0 m<h ≤ 4 m, the stable value of water content in all parts is higher, approximately 28% in the inverted arch and arch foot, and approximately 25% in the arch waist and arch crown. The upper part is smaller whereas the lower part is larger. When 4 m<h<8 m, the stable value of soil moisture content begins to decrease with the increase of h. When h ≥ 8 m, the stable value of water content in each part is basically the same and remains unchanged with the increase of h.
  • Model Test and Discrete Element Analysis of Soil and Water Loss Induced by Joint Leakage of Shield Tunnel
    ZHANG Zhi-guo, CHENG Zhi-xiang, ZHANG Meng-xi, MA Shao-kun, CHEN Jie, WU Zhong-teng, LI Yun-zheng
    China Journal of Highway and Transport. 2023, 36(1): 162-175. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.014
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    The leakage of shield tunnel joints is the main factor in ground subsidence, and controlling the law for the soil and water loss development is the basis of methods to prevent the risk of ground subsidence. Based on the critical crack width, the settlement law of a sand layer and the influencing factors of the pore water pressure change law were analyzed using model tests for different crack positions, different overburden depths, and different overlying water levels. A set of seepage tracing devices was designed to investigate the distribution of a seepage field and change law of a streamline trajectory. The test results showed that the settlement of a sand layer was more obvious at a shorter vertical distance from the leakage, and the collapse area gradually diffused to the surface from the area around the leak, developing from a deep "V" type to shallow "V" type and "gauss curve type." When the leakage joint was closer to the bottom of the arch, the settlement of the sand surface and dissipation of the pore water pressure were smaller. When the depth of the overlying soil was higher, the sand settlement was smaller, disturbance range was narrower, and dissipation of the pore water pressure was greater. When the overlying water level was higher, the sand settlement was greater, disturbance range was wider, and dissipation of the pore water pressure was greater. The tracer streamline was a series of circular arcs, and five streamlines flowed to the leak slot. The flow velocity of the water far from the leak slot was slow, which produced a longer streamline, and the downward development of the tracer streamline accelerated the penetration to the leak slot streamline. In addition, the arching effect of sandy soil and displacement evolution law during the process of seepage erosion were analyzed by constructing a numerical model of the sandy soil of the tunnel as a discrete element. This study revealed the influence of sand particle migration and loss around a shield tunnel on the mesoscale of the surrounding environment. The discrete element analysis showed that there was no leakage in the joint, and no seepage erosion passage. The soil arch around the joint was stable, and once leakage occurred, the soil arch was immediately destroyed, which was the beginning of the soil and water loss in the model test. The entire soil and water loss process was always accompanied by the following process:"sand particles arching → soil arching failure → soil arching regeneration → soil arching continued failure." Finally, a stable soil arch was formed around the leakage joint, and the phenomena of the sand leakage stopping and sand layer displacement convergence in the model test were reasonably explained.
    • Traffic Engineering
  • IntelliWay: An Integrated Architecture and Testing Methodology for Intelligent Highway Using Varied Coupling Modularization
    ZHAO Xiang-mo, GAO Ying, XU Zhi-gang, CAO Yi-zhe, GONG Si-yuan, LI Li, LIU Zhi-guang, ZUO Zhi-wu, WANG Fu-hai, SUN Hao, ZHU Xiao-dong, RUI Yi-kang, LIU Zhan-wen, WANG Guan-qun, LIU Cheng-lin, ZHANG Qian, LIU Peng
    China Journal of Highway and Transport. 2023, 36(1): 176-201. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.015
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on the development of intelligent highways, typical logical and physical models of cooperative vehicle-infrastructure systems are summarized in this paper. Through the comparative analysis of demand between cooperative vehicle infrastructure systems on highways and other advanced transportation systems, intelligent highway systems can be better studied. After summarizing the overall architecture of domestic and foreign cooperative vehicle infrastructure systems on highways, this paper proposes a novel generation method for intelligent highway system architectures, including an overall architecture, intelligent classification, and data distribution mechanism for intelligent highways based on modularization. Additionally, according to the current mainstream application technology of cooperative vehicle infrastructure systems on highways, the status of research on emerging technologies driving the rapid development of intelligent highway systems is summarized. Research topics include high-precision vehicle navigation technology, advanced driver assistance system and vehicle bus technology, roadside unit optimization technology, heterogeneous network integration technology, network load balancing technology, network information security technology, multi-sensor fusion and cooperative awareness technology, user-centered scene adaptive information publishing technology, vehicle group cooperative autonomous driving technology, forecasting of transportation technology based on big data and artificial intelligence, lane-level active traffic management technology, and component-based application service development technology. Based on the characteristics of these 12 key technologies, recommendations regarding the application and promotion of intelligent highway system technology in the future are presented. In this study, typical scenarios of cooperative vehicle infrastructure systems on highways were analyzed, including traffic information services in broadcasting, active traffic management, syndrome traffic information services, automated vehicle dedicated lanes, and cooperative autonomous driving in vehicle platoons. Additionally, evaluation methods and relevant case studies on intelligent highway systems are summarized. Finally, the challenges and future development trends of intelligent highways are systematically analyzed and predicted. Highly trusted information interactions and intelligent collaborative control between people, goods, vehicles, roads, and clouds will provide a real-time and highly reliable traffic environment for autonomous driving on highways. The results of this study are significant as a reference for current and future technology research and the development of intelligent highways and engineering applications of intelligent highway systems.
  • Layout Optimization of Static Wireless Charging Facilities for Electric Bus Routes with Dedicated Bus Lanes
    BIE Yi-ming, HAO Ming-jie, WANG Lin-hong
    China Journal of Highway and Transport. 2023, 36(1): 202-213. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.016
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To reduce the layout cost of static wireless charging (SWC) facilities for electric bus routes and improve the utilization of time control points, this paper presents an optimization method for the locations of SWC facilities considering the impact of time control points. First, a model for describing the electric bus operation state was established, and a calculation method for estimating the increase in the passenger travel time cost was proposed. Second, under the constraints of the total relax time, remaining battery power, and punctuality rate, an optimization model for the SWC facility layout was developed for the bus route with dedicated bus lanes. The objectives of the model were to minimize the cost of layout and the increase in the passenger travel time cost, and maximize the effective stop utilization rate. The optimization variables were whether each stop was equipped with SWC facilities or operated as a time control point, and the corresponding relax times. The proposed model was solved by the sparrow search optimization algorithm embedded with stochastic simulation technology. Finally, a real bus route was taken as an example to verify the developed model, and a sensitivity analysis of the battery capacity and charging power was conducted. The results show that within the power demand of different bus trips, the total layout cost of charging facilities and the increase in the passenger travel time cost decrease with an increase in the battery capacity or charging power. Additionally, the total layout cost of charging facilities changes in a gradient descent manner.
  • Hybrid Fully-actuated Signal Control and Transit Signal Prioritization at Intersections with Contraflow Left-turn Lanes
    XU Hong-feng, CHEN Hong-jin, ZHANG Dong, LU Qian-hui
    China Journal of Highway and Transport. 2023, 36(1): 214-225. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.017
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Intersections with contraflow left-turn lanes (CLLs) have been applied across more than 70 cities in China. However, there are no uniform requirements for installing and operating traffic control devices at such intersections. It is a necessity to consider how to implement transit signal priority at intersections with CLLs when bus-only lanes traverse them. In this study, we developed a hybrid fully-actuated signal control and transit signal priority (FASC+TSP) for intersections with CLLs. Specific requirements for traffic signal installation, signal phase allocation, phase sequence selection, and traffic flow data detection were presented. The goals of FASC+TSP were to eliminate the traffic safety risk of CLLs, expedite the operating speed of prioritized vehicles, and reduce the wasted green time of vehicle phases. Five groups of logic rules were designed to form the signal control algorithm of FASC+TSP. Green extension and early green could be offered to prioritized vehicles. The green time of vehicle phases, and the red and green times of pre-left-turn phases were automatically adjusted. Vissim was used to establish virtual road traffic environments for a typical four-leg conventional intersection and an intersection with CLLs that was reconstructed from the conventional one. In the traffic simulation experiments, a D-optimal design was used to generate 1 000 heavy-load demand scenarios. A total of 3 000 simulation runs were conducted. The experimental conclusions are two-fold. First, for the test-bed intersections applying fully-actuated signal control, the presence of CCLs has a statistically significant impact on the intersection operational performance. CCLs strongly reduce the average delay of all vehicles, and to a certain degree, reduce the average delay of prioritized vehicles. Second, for the test-bed intersection with CCLs, upgrading fully-actuated signal control to FASC+TSP has a statistically significant impact on the intersection operational performance. FASC+TSP shows strong effectiveness in reducing the average delay of prioritized vehicles. Meanwhile, the average delay of all vehicles will not noticeably increase or even frequently decrease.
    • Automotive Engineering
  • Vehicle Trajectory Prediction Based on Spatial-temporal Attention Mechanism
    LI Wen-li, HAN Di, SHI Xiao-hui, ZHANG Yi-nan, LI Chao
    China Journal of Highway and Transport. 2023, 36(1): 226-239. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.018
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Vehicle movements can be highly random, and the driving style used becomes complex in urban traffic environments. To overcome the difficulties in accurately predicting vehicle trajectory in complex traffic environments, the Social Generation Adversarial Network (Social GAN) machine-learning model was used to develop a vehicle trajectory prediction algorithm named SIA-GAN. This developed algorithm was based on a spatial-temporal attention mechanism by considering a vehicle's speed, acceleration, course angle driving state, and shape size, and an interaction influence force field between the different vehicles was derived. Based on the magnitude of the interaction influence force that characterized each vehicle at the scene, different spatial attention weighing factors were assigned to the vehicles, along with a component of stressed "attention" that incorporated the information of vehicles having a greater impact on each other's driving pattern. The time attention mechanism was then combined to mine the time dependence of the vehicle under consideration in terms of the trajectory's feature vector during the observation period. To verify its effectiveness, the proposed algorithm was iteratively trained on an open-source dataset and compared with three trajectory prediction algorithms (long short-term memory (LSTM), Social LSTM, and Social GAN). The results show that SIA-GAN not only improves the convergence speed during training but also significantly reduces the average displacement error (ADE), final displacement error (FDE), average velocity error (AVE), and average course angle error (ACAE) when compared with other existing algorithms for trajectory prediction. At predicts 3.2 s, each of the aforementioned indexes decreases by 51.25%, 60.1%, 37.84%, and 13.75%, respectively, on average. The average reduction at predicts 4.8 s is 52.78%, 61.47%, 35.92%, and 9.57%, respectively. Thus, the proposed SIA-GAN trajectory prediction algorithm can accurately and effectively reflect complex spatial interaction characteristics between vehicles, enhancing the accuracy, rationality, and interpretability of trajectory predictions.
  • Clothing Color of Vulnerable Groups for Intelligent Vehicle Testing
    HAN Ling, ZHU Chang-sheng, CHI Rui-feng, FANG Ruo-yu, ZHANG Hui, LIU Guo-peng, YI Qiang
    China Journal of Highway and Transport. 2023, 36(1): 240-252. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.019
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The testing of intelligent vehicles is paramount to their technological development and application. Whether the test surrogates can accurately reflect the characteristics of the traffic objects in the actual road environment of in-field testing is key to ensuring the credibility of the evaluation results. Meanwhile, the clothing color of vulnerable groups on the road is a key parameter for designing the vulnerable group surrogates as well as a main indicator in the relevant standards for intelligent vehicle evaluation. By analyzing major traffic accident in one representative province in China from 2018 to 2020, a sample of 178 victim cases is obtained. Firstly, the clothing color of the samples is extracted. Subsequently, the appropriate color space is converted from RGB (Red-Green-Blue) space to LUV (Brightness, Chroma) space. Using the conversion result as the clustering parameter, the K-means clustering algorithm is applied to obtain the representative clothing color based on different factors such as age, season, and travel mode. Different from the clothing color combination of a black tops/blue pants of the surrogates in the current European standard, a black tops and black pants combination is more representative of the scenarios in China. To conform to China-New Car Assessment Programme (C-NCAP) regulations, multiple Near and Far scenarios with black tops and black pants of pedestrian surrogate and bicyclist surrogate are constructed respectively. The collision points between the testing vehicle and surrogate at 25%, 50% and 75% of the bumper of the testing vehicle in the corresponding scenarios are analyzed to evaluate the response ability of the intelligent vehicle equipped with an automatic emergency braking system. The results show that in all scenarios, the testing vehicle can successfully identify the target and brake actively. These tests verified the feasibility and effectiveness of the black tops/black pants combination under the current testing standards. The results provide sufficient data support for intelligent vehicle testing, improve relevant standards and regulations in the transportation industry, and promote the development of intelligent vehicle testing technology.
  • Analytical Modeling of Air-gap Magnetic Field and Multi-objective Optimization of Interior Permanent Magnet Synchronous Motor for Electric Vehicles
    AN Yuan-sheng, MA Cong-gan, LI Xin, SHEN En-de, YU Dong-lei
    China Journal of Highway and Transport. 2023, 36(1): 253-262. https://doi.org/10.19721/j.cnki.1001-7372.2023.01.020
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To improve the analytical calculation accuracy and optimization efficiency of the air-gap magnetic field of an interior permanent magnet synchronous motor (IPMSM) for electric vehicles, a parametric analytical model of the air-gap magnetic field considering the saturation effect of rotor core magnetic bridges was established using a hybrid analytical method. First, an analytical model of the open-circuit air-gap magnetic field of an IPMSM was established using the subdomain method combined with the equivalent magnetic circuit method. A virtual magnetic field analytical model of the rotor magnetic bridge was established by the same method. An armature reaction magnetic field analytical model considering the saturation effect of the rotor magnetic bridge was obtained, and an analytical model of the load air-gap magnetic field of the IPMSM was established by the superposition principle. The accuracy of the analytical model was verified using the finite element method and a torque test. Compared with the experimental results, the analytical calculation error is less than 5%. The calculation time is reduced by more than 90% compared with the finite element simulation. Based on the established analytical model, the optimization variables are the pole arc width of the permanent magnet, width of the stator slot, and thickness of the magnetic bridge at the end of the rotor. Taking the radial force wave of specific order frequency, torque, and efficiency as the optimization objectives, a multivariable and multi-objective optimization of an IPMSM prototype for electric vehicles was carried out using the non-dominated sorting genetic algorithm with elite strategy (NSGA-II). After optimization, the radial force wave of the specific-order frequency of the motor reduces by 9.2%, the maximum torque increases by 2.49%, the maximum efficiency increases by 0.69%, and the area of the high-efficiency zone increases by approximately 54.46%. The results show that the proposed method solves the common difficulties of analytical modeling of IPMSM with strong nonlinearity and high saturation and considerably improves motor multi-objective optimization efficiency. This research can provide a reference method for the optimization design of an IPMSM for electric vehicles.
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