20 May 2017, Volume 30 Issue 5
    

  • Select all
    |
  • Research on Performance of New Pavement Drainage System Under Rainfall Infiltration
    LIU Yu-chuan, MIAO Hong-jie
    China Journal of Highway and Transport. 2017, 30(5): 1-9.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to ensure the fast and effective drainage of pavement structure, a new drainage system of pavement structure made up of geocomposite drainage materials was proposed based on unsaturated seepage theory, including the hydraulic transport layer, capillary barrier layer and isolation layer from top to bottom. The model test and numerical simulation analysis of new pavement drainage system were carried out to investigate the drainage performance of new pavement drainage system under the condition of rainfall infiltration. In the model test, tensiometers in the base and subgrade monitored the suction change. An unsaturated seepage numerical analysis model was established to analyse the effects of thickness, slope and position of new drainage system on the drainage performance of pavement structure by the control variable method. The results show that water seeping through the pavement is drained away quickly and effectively by new drainage system. Base material has always been unsaturated in the whole test process and base suction starts to rise ten minutes after the rain stops. The new drainage system can prevent the water infiltration to subgrade with subgrade suction keeping at the initial value. In terms of the new drainage system, the volumetric water content of the base increases constantly in the rainfall without reaching the saturation volume moisture content. After the rain stops, the volumetric water content of the subgrade decreases slightly while the volumetric water content of subgrade remains the same. The construction of new pavement drainage systems between surface course and base, base and subgrade respectively has advantage of controlling the suction and volumetric water content of base.The water content of the base material decreases and the bearing capacity of the base increases to a certain extent with the increase of the thickness and slope of the new drainage system. The results provide the theoretical basis for application of the new pavement drainage system.
  • Analysis of Stability of Carbonaceous Mudstone Embankment After Disintegration Pretreatment During Process of Water Level Fluctuation（in English）
    ZENG Ling, QIU Xiang, FU Hong-yuan, TANG Hao-long, LI Guang-yu
    China Journal of Highway and Transport. 2017, 30(5): 10-19.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to research the carbonaceous mudstone embankment stability during the period of water level fluctuation, on the basis of exploring the influence factors of embankment stability, an evaluation method of embankment stability which simultaneously considered the water pressure in front of slope, pore water pressure, pore water gravity, seepage force, softening, and unsaturated strength was proposed by combing the basic theory of seepage and stability analysis and seepage characteristics and stability of carbonaceous mudstone embankment during the water level fluctuation were calculated. The results show that the embankment stability evaluation method presented in this paper with a strong applicability and pertinence can comprehensively evaluate the carbonaceous mudstone embankment stability with the influence of multiple factors. During the water level rising stage and the high water level constant stage, the water table, pore water pressure and saturation in the interior embankment rise gradually. The ascending range of pore water pressure is inversely proportional to the elevation but the increasing amplitude of saturation is proportional to the elevation. The horizontally inward and vertically downward seepage force, peak, and the horizontally inward displacement increase first and then decrease but vertically upward displacement increases constantly. During the water level falling stage and the low water level constant stage, the water table, pore water pressure, saturation of the interior embankment gradually decrease. The decreasing range of pore water pressure is inversely proportional to the elevation but the decreasing amplitude of saturation is proportional to the elevation. The horizontally outward seepage force and its peak, the horizontally outward and vertically downward displacement as well as plastic zone area increase first and then decrease with the vertically downward seepage force in “Ƨ” shape. The research results provide references for the construction and stability control of the carbonaceous mudstone embankment of the reservoir and river area.
  • Test on Failure Characteristics of Pressure-type Anchor with Lattice Beam Under Earthquake（in English）
    HAO Jian-bin, WANG Ban-qiao, LI Nan
    China Journal of Highway and Transport. 2017, 30(5): 20-27,37.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To investigate the seismic behavior and failure characteristics of slope anchorage system under strong earthquake, Wenchuan wave, EL-Centro wave and sinusoidal wave were regarded as the seismic excitation in the shaking table model test. The dynamic response difference of landslide under strong earthquake and mechanical behavior of anchor and lattice beam at different locations were investigated. The results show that under strong earthquake, the form of shear relaxation zone gives rise to slope toe first entering into the plastic zone. At the same time, the bearing capacity of anchors at slope toe is affected and horizontal beams at the slop toe become bended and deformed. Because of a potential sliding surface on the slope, the upper part of the slope is prone to form tensile failure area and the tension of anchors in the first column at the top of slope increases. Thus the discordance of upper lattice beams and anchors is obvious and bending deformation occurs in horizontal beams at the top of slope. The bending strains of vertical beams are lower than those of horizontal beams and the differences of bending strains in each vertical beam are not notable, in good coordination with anchors. On the basis of pseudo-static method design, it is advised that short anchors or soil nails are driven into slope toe to balance the uncoordinated reciprocating motion at sliding surface near slope toe. In order to prevent tension crack near the sliding surface, top anchors should be lengthen in design. Short anchors and micro piles are vertically driven into top surface of slope or plants with roots flourishing are cultivated to protect the slope. The stretch bending deformation of horizontal beams should be emphatically considered in design.
  • Embankment Seismic Fragility Assessment Based on IDA-PSDA
    YIN Chao, SHI Jun, LIU Fei-fei, TIAN Wei-ping, TIAN Wei
    China Journal of Highway and Transport. 2017, 30(5): 28-37.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to reveal the characteristics of embankment fragility under seismic actions and investigate the influence of retaining walls on embankment seismic fragility, seismic fragility was theoretically evaluated in view of the K1125+470 embankment of Xi'an-Baoji segment in Lianyungang-Huoerguosi expressway. Embankment seismic fragilities were ranked and seismic damage parameters were selected. The corresponding relationship between embankment seismic damage levels and seismic damage parameters as well as the finite-difference models of embankments with and without a retaining wall based on Flac was established. The actual seismic oscillation records were selected for the Incremental Dynamic Analysis, clarifying regularity of seismic damage parameters under the effect of peak ground acceleration with and without a retaining wall. Probability of seismic damage at different grades was investigated on the basis of probabilistic seismic demand analysis and the seismic fragility curves were also mapped. The comparison was made for the seismic fragility assessment results of the embankments with and without a retaining wall. The results show that when peak ground acceleration reaches 1.2g, the probabilities of destruction to the embankments with and without a retaining wall are 16.854% and 76.679% higher than the probability with the peak ground acceleration of 1.0g on average, 95.895% and 88.008% higher than the probability with the peak ground acceleration of 0.8g on average. Whether the retaining wall exists or not, the greater the peak ground acceleration is, the greater the probabilities of severe embankment seismic damage are. When the transcendental probabilities of destruction damage are 30%, 50% and 80%respectively, ground peak accelerations corresponding to destruction of embankment with a retaining wall are 17.93%, 18.14% and 18.34% respectively higher than those without a retaining wall, namely, under the same seismic actions, the seismic damage status of embankment without a retaining wall is more serious than that with a retaining one, with a positive effect of a retaining wall on embankment seismic performance.
  • Cyclic Shear Behavior on Soil-geogrid Interface of Sandwich Reinforced Soil
    LIU Fei-yu, ZHANG Tao, SHI Jing
    China Journal of Highway and Transport. 2017, 30(5): 38-43.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Aiming at the paucity of research on the effect of cyclic shear on shear behavior of reinforced soil interface, a series of cyclic direct shear tests of Sandwich reinforced soil were performed by a large-scale direct shear device. The effect of shear rate, thickness of thin sand layer, cyclic shear amplitude and vertical stress on the cyclic shear behavior of Sandwich reinforced soil was investigated by Geogrid, Fujian standard sand and remolded clay with 28% water ratio, when the vertical stresses were 30, 60 and 90 kPa respectively and the shear displacement amplitudes were 3, 6 and 9 mm respectively with shear rates of 1, 2, 5 and 10 mm·min-1 respectively as well as the thickness of thin sand layer being 4, 6,8, 10, 12 and 14 mm respectively. The results show that when the thickness of thin sand layer increases from 2 mm to 14 mm, the peak shear stress on soil-geogrid interface increases from 54.3 kPa to 67.9 kPa and then decreases to 59.4 kPa. When the thickness of thin sand layer is 8mm, the peak shear stress on soil-geogrid interface reaches a maximum value, namely, 67.9 kPa. When the shear rate is 1 mm·min-1, soil-geogrid interface mainly shows the shear hardening. The increase amplitude of the peak shear stress is large in the first few cycle numbers and gradually decreases with the increase of cycle number. When the shear rate is more than 1 mm·min-1, the shear softening phenomena begin to appear on soil-geogrid interface and the more obvious the phenomena become, the higher the shear rate is. With shear amplitude increasing from 3 mm to 9 mm, the alternation of shear dilatation and contraction becomes more and more obvious and the final value of shear contraction increases with the increase of shear amplitude. When the vertical stresses are 30, 60, 90 and 120 kPa, the corresponding peak shear stresses on soil-geogrid interface are 32.6, 43.2, 60.4 and 82.9 kPa respectively, which show that the peak shear stress on soil-geogrid interface increases with the increase of vertical stress.
  • Urban Road Soil Subgrade Disease Recognition by Kernel Matching Pursuit
    QIAO Xu, ZHAO Xue-jun, YANG Feng, ZHENG Jing
    China Journal of Highway and Transport. 2017, 30(5): 44-51.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to accurately recognize the road soil subgrade disease to avoid the occurrence of collapse on the road, ground penetrating radar (GPR) was always used to detect the urban road. In allusion to universal law of road soil subgrade disease on the non-hardened and hardened road, firstly, one-dimensional filtering of GPR images was carried out by Wiener filter and GPR images were obtained by smoothing the gain function in cepstrum domain. Secondly, the results of the GPR images in different transform domains were obtained by Fourier transform, wavelet transform and so on. Based on kernel function dictionaries including Fourier kernel function, polynomial kernel function, matching pursuit of GPR images in different transform domains was carried out. Finally, according to the comparison of different kernel matching pursuit (KMP) sequences, the sensitive sequences of the road soil subgrade water disease and empty hole were found out and the type of urban road soil subgrade damage would be recognized. The KMP sequences were compared based on correlation coefficient algorithm and the area where urban road base damage occurred was found. The results show that the type and range of disease are consistent with the actual situation, and water disease and empty hole can be recognized efficiently. The validity of algorithm is verified by GPR data sets of urban road with the accuracy of identification reaching more than 99%. The KMP algorithm, a method of handling the GPR images, will contribute to the city road soil subgrade damage recognition to avoid the occurrence of road collapse.
  • Evaluation Indexes of Asphalt Mixture Main Skeleton Based on Digital Image Processing
    SHI Li-wan, WANG Duan-yi
    China Journal of Highway and Transport. 2017, 30(5): 52-58.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to provide a reference for gradation design and optimization of skeleton dense structure asphalt mixture to form good rut resistance performance for designed asphalt mixture, in allusion to the shortage of current asphalt mixture skeleton structure criterion, calculation method was optimized by considering the contact characteristics of coarse aggregates through digital image processing technique based on the analysis of existing evaluation index of asphalt mixture skeleton structure. Compared with the microscopic distribution characteristics of coarse aggregate contacts in asphalt mixture with four different gradations, the correlation between microscopic quantitative evaluation indexes and macroscopic evaluation indexes was analyzed and the microscopic qualitative and quantitative evaluation indexes and criteria for the coarse aggregates were proposed to form an optimal main skeleton. The results show that values obtained by the optimal calculation method of VmixVCA(I) are about 15%-20% larger than values based on current experience method and more strict and reasonable skeleton discriminant can guarantee interlocked coarse aggregates to form an optimal main skeleton. There is a good correlation between microscopic quantitative evaluation indexes and macroscopic evaluation indexes of asphalt mixture, with microscopic quantitative evaluation indexes representing the rut resistance performance. During the design process of skeleton dense structure asphalt mixture, the average coordination number increases and the C value decreases by adjusting the gradation, with effective improvement of microscopic indexes and the quality of the main skeleton, so the designed asphalt mixture shows good rut resistance performance. The qualitative and quantitative evaluation indexes of the optimum main skeleton structure formed by coarse aggregate are: i>VDRCVCA，n>1.6 while C<20%.
  • Research on Application Performance of Warm-mixed Flame Retardant Asphalt and Asphalt Mixture
    WANG Da-wei, DENG Xiang-ming
    China Journal of Highway and Transport. 2017, 30(5): 59-66.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to grasp practical application effect of warm-mixed flame retardant asphalt mixture, the influences of warm-mixed agent and flame retardant agent on warm mix, flame retardant and regular performance were firstly analyzed based on limiting oxygen index and viscosity test and then the technical performance of warm-mixed flame retardant asphalt mixture was investigated by cone calorimeter. The durability of warm-mixed flame retardant asphalt pavement was verified by the accelerated loading test. The results show that there exist obvious warm-mixed effect of Sasobit on SBS modified asphalt and obvious flame retardant effect on FRMAXTM, without any interference. Based on Sasobit, high temperature performance of SBS modified asphalt is improved and low temperature performance drops. However, FRMAXTM has a negative effect on both high temperature and low temperature performance of warm-mixed asphalt, without storage stability being influenced. Flame retardant and smoke suppression performances of SBS modified asphalt can be significantly improved by FRMAXTM, and Sasobit is detrimental to the flame retardant performance of flame retardant asphalt mixture, but with improvement of the smoke suppression performance. With no influence of Sasobit and FRMAXTM on high temperature stability of SBS modified asphalt mixture, low temperature crack resistance and water stability slightly decrease and anti-fatigue performance declines. Warm-mixed flame retardant asphalt pavement structure shows a good durability on rutting resistance and anti-slide performance.
  • Research on Plastic Hinge Length of Externally Prestressed Concrete Box Girders with Corrugated Steel Webs（in English）
    DU Jin-sheng, FENG Jian-xiang, BIAN Xiao-long, WU Pei-lin, XU Qiang, SONG Jian-yong
    China Journal of Highway and Transport. 2017, 30(5): 67-73.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to investigate the plastic hinge length of externally prestressed concrete box girders with corrugated steel webs, the finite element numerical calculation combined with the existing test data was adopted to determine the internal force redistribution and plastic deformation ability of the girders under failure load such as earthquake. The nonlinear finite element numerical model of externally prestressed concrete box girders with corrugated steel webs was established based on OpenSees platform and verified from the aspects of failure loads, mid-span deflections, stress increments in external tendons and concrete compressive strains by experimental data from two researchers. In addition, the effects of numerical models with or without considering shear deformation on the box girder deflection were comparatively analyzed. Parametric analysis was carried out to investigate factors that may affect the plastic hinge length of externally prestressed concrete box girders with corrugated steel webs. Finally, through comparing the calculation results of existing equations and simulated results, an equation for estimating the plastic hinge length was recommended for externally prestressed concrete box girders with corrugated steel webs. The results show that the effect of shear deformation on deflection of externally prestressed concrete box girders with corrugated steel webs can be neglected in practical computation. The shear span ratio and the effective prestress have significant impact on the plastic hinge length of externally prestressed concrete box girders with corrugated steel webs, while the reinforcement steel area of tensile zone and the concrete compressive strength have relatively limited effect on the plastic hinge length.
  • Influences of Precast Segmental Connector Forms on Seismic Performance of Bridge Pier
    WANG Zhi-qiang, WEI Zhang-zhen, WEI Hong-yi, WANG Hao
    China Journal of Highway and Transport. 2017, 30(5): 74-80.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to research seismic performance of precast segmental bridge pier with grouted sleeve and grouted sylphon, and to validate the design of new-built Jia Min north urban viaduct in Shanghai，two precast pier specimens with different connectors and one cast-in-place pier specimen were used to conduct pseudo-static tests. The dimension scale of three specimens with the same shear span ratio was 1∶3. The uniaxial low-frequency cyclic loads were used as horizontal loads in the form of displacement control. Each load level consisted of 3 loops. Specimens were collapsed due to increasingly horizontal action under the same axial force. Failure mode and damage parts of precast concrete bridge piers under two kinds of segment constructions were compared by qualitative observation and quantitative data analysis. And their seismic performance was summarized by analyzing hysteresis curves, skeleton curves, stiffness, ductility, energy dissipation and residual deformation. The results show that the damage of segmental piers with grouted sleeve and grouted sylphon on the cap surface focus on the interface of pier and cap. The displacement ductility of the grouted sylphon with higher equivalent damping ratio is better than that of grouted sleeve while the residual displacement of sleeve one with great equivalent stiffness is minor. Various performance parameters of two precast segmented bridge pier models are similar with those of cast-in-place specimens, meeting the demand of seismic requirements from moderate to high earthquake zones.
  • Calculation Method of Adjustments of Anchor Span Cable Forces and Saddle Angle for Long-span Suspension Bridge
    SHEN Rui-li, WANG Yuan, WANG Tao
    China Journal of Highway and Transport. 2017, 30(5): 81-88,103.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to adjust the anchor span cable forces and the saddle angle of long-span suspension bridge in security and high speed, the calculation method of adjustments of anchor span cable forces and the saddle angle was investigated, considering the special property intercoupling between anchor span cable forces and the saddle angle at cable finished stage. Under the hypothesis of the small deformation, the translational stiffness of the saddle IP in the direction of the slip plane was calculated, taken structural characteristics of long-span suspension bridge into consideration. Based on the mechanical equilibrium condition of the saddle IP, the influence matrix of anchor span cable strands was deduced and object functions for adjustments of the anchor span cable forces and the saddle angle could be uniformly expressed by the elastic elongation and saddle angle. In virtue of the numerical simulation software, a numerical iterative method was used to compute the ideal adjustment of the anchor span cable strands and saddle angle for long-span suspension bridge. By numerical simulation results, the optimization methods of the adjustment order and amounts of anchor span cable strands were proposed. The results show that adjusted cable forces computed by the influence matrix of anchor cable are in agreement with the measured ones. Meanwhile the theoretical errors of the final cable forces are less than 0.1 kN, which are calculated by the ideal cable adjustment scheme, and the cable forces have been not too large or too small in the adjustment process. The calculation method can not only theoretically satisfy the anti-slip requirement, but also adjust the anchor span cable forces and the saddle deflection effectively, with practical value for engineering.
  • Condition Assessment of Bridge Scour by Tracing Dynamic Performances of Bridges
    XIONG Wen, Zou Chen, YE Jian-shu
    China Journal of Highway and Transport. 2017, 30(5): 89-96.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to improve the economical efficiency and convenience during the bridge scour assessment, a theory of analyzing the bridge scour condition by tracing the dynamic performances of bridges was proposed. Based on the natural frequencies of vibration and modes of vibration after filtering, a structural flexibility matrix was established reflecting the bridge condition. Using such flexibility matrix, “calculatedly structural displacement discrepancy” was deduced based on a concerned direction of structural stiffness as an identification parameter of bridge scour. A quantitative relationship between the identification parameter and scour depth was then obtained after a series of parametric analysis. Meanwhile the actual value and dynamic performance were obtained during the bridge routine detection and measurement. Therefore, based on the pre-obtained relationship between structural displacement difference and scour depth, the bridge scour depth at the moment of monitoring was calculated corresponding to the practical value. Finally a simple support bridge was used to demonstrate the specific application methods and steps for the proposed condition assessment method of bridge scour in terms of identification of dynamic characteristics. The pile-soil springs along different directions were established based on the code of American Petroleum Institute (API). The bridge scour was simulated by sequentially removing the springs. The prerequisite of the proposed method in the real engineering was further given. The results show that the identified scour depths are equipped with acceptable accuracy and the coupling effects among different piers can be amended by fitting formulas. The qualitative and quantitative analysis of bridge scour in virtue of conventional project of bridge inspection has advantages of computational logic, convenience and economy of monitoring equipment. The scour depth can be correctly predicted as long as the dynamic performances of bridges are accurately measured and traced.
  • Hot Spot Stress Method for Fatigue Life Assessment of Welded Joints Under Complex Stress Fields
    JIE Zhi-yu, LI Ya-dong, WEI Xing, XIAO Dong-tao, LIU Mao-kun
    China Journal of Highway and Transport. 2017, 30(5): 97-103.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to investigate the effect of complex stress fields on fatigue life of welded joints, axial tension fatigue tests and finite element numerical simulation were carried out for full penetration load-carrying fillet cruciform welded joints with different inclined angles (θ=0°, 15°, 30°, 45°). The linear extrapolation method, the quadratic extrapolation method and the 1 mm method were used to calculate hot spot stresses of weld toes. The suitable mesh sizes were determined by finite element mesh sensitivity analysis and concentration factors of hot spot normal and shear stress varying with inclined angles were obtained. Fatigue lives of welded joints were assessed based on the equivalent stress method, the interaction equation method and the bi-parametrical critical plane method and compared with test results. The results show that when the minimum mesh size is less than 0.1t and 0.03t, the influence of mesh size on hot spot stresses calculated by the extrapolation method and the 1 mm method respectively can be ignored. Concentration factors of hot spot shear stress are larger than those of normal stress. Fatigue life increases with the increase of inclined angle and when inclined angles are 15°, 30° and 45° respectively fatigue life test results are 1.26, 1.52 and 2.38 times larger than fatigue life at θ=0°. When inclined angles are 30° and 45° respectively, the errors of fatigue lives predicted by the interaction equation method and the bi-parametrical critical plane method are relatively large but the least conservative. However, fatigue lives predicted by the equivalent stress method are in good agreement with test values with sureness. Thus, it is recommended to use the linear extrapolation method to calculate hot spot stress and the equivalent stress method to predict fatigue life of welded joint under complex stress fields.
  • Numerical Simulation of Wind Field on Bridge Site Located in Mountainous Area and Gorge Based on WRF
    SHEN Lian, HAN Yan, DONG Guo-chao, CAI Chun-sheng, ZHANG Jian-ren
    China Journal of Highway and Transport. 2017, 30(5): 104-113.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to resolve the difficulty in providing reasonable inlet boundary conditions for the numerical simulation of wind field in mountainous area, the multiscale coupling method was adopted for accurately simulating the wind field on the bridge site at mountainous area based on a meteorological software of weather research and forecast (WRF). Firstly, at the process of simulation, the multiscale coupling method was adopted to obtain the mesoscale velocity field information by the WRF. Secondly, the coupling surface was divided into several pieces based on the principle of wind fluctuating degree in the inlet boundary. Block polynomial interpolation (BPI) fitting method was used to fit the wind velocity, and then the fitting velocities were given to the inlet boundary of the large eddy simulation (LES) by the UDF program. Finally, taking the Lishui Bridge in Zhangjiajie as the research background, the wind velocities real-time observation stations were established at the bridge site for a comparison purpose. The measured results were compared with the numerical simulation results by the proposed method. The results show that the computational results of WRF can be well applied to the inlet boundary of wind field CFD numerical simulation in mountainous area after downscaling. The method can provide a reasonable value of average wind in inlet boundary for the numerical simulation in mountainous gorge area. Meanwhile, the BPI method provides a good solution to the irrational inlet problems caused by the “artificial cliff”. The distributions of parameters including the average wind velocity, wind direction and wind attack angle can be accurately obtained by the proposed method.
  • Development and Application on Mined Tunnel Seepage Model Test System for Construction and Operation Period
    HE Chuan, LI Zheng, YANG Sai-zhou, LUO Yao-wen, YANG Wen-bo
    China Journal of Highway and Transport. 2017, 30(5): 114-121,131.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to explore the relationship between the waterproof and drainage system of tunnel and the underground seepage field, a seepage model test system of mined tunnel for construction and operation period was developed, including a seepage model box, a simulation device of reinforced area, a collecting device of water discharge, a mobile circulating water tank and a data acquisition device. The length, height and width of model test system were 3 m, 3 m and 2 m respectively. It was convenient and accurate to test the water pressure, water discharge and seepage field changes of mined tunnel during construction and operation period. For different test requirements, this system can be feasible to change and configure surrounding rock, grouting circle, pre-grouting area on tunnel face and initial lining under different water heads and the real state of tunnel as well as its surrounding seepage field should be restored as much as possible. Based on the actual engineering, the seepage model test system, along with the new type of simulation material of surrounding rock-support system in view of controlling permeability coefficient, was applied to carry out seepage model tests under different permeability coefficients of grouting circles. The results show that with the decrease of permeability coefficient of the grouting circle, the seepage velocity slows down but the seepage time increases dramatically. The water pressure distribution laws of characteristic points behind the secondary lining and the grouting circle are similar during the operation period. The smaller the permeability coefficient of the grouting circle is, the more obvious the effect of bearing water pressure can be. For characteristic points of the vault of tunnel under the condition of non-disturbed excavation, the water pressure decreases rapidly when the excavation area closes to the tunnel face, but there is the effect of dynamic water pressure. The change of permeability coefficient of grouting circle has limited effect on seepage in the surrounding rock in front of the tunnel face. For the characteristic points of the arch bottom of tunnel in the non-disturbed excavation, the dispersion of each measurement point is large under different permeability coefficients of grouting circles. With the increase of permeability coefficients of the grouting circle, the water pressure behind the initial lining gradually increases but the water pressure value behind the grouting circle is in a downward trend.
  • Formation Mechanism of Urban Traffic Carbon Emissions Based on Mobile Monitoring: Case Study of Shanghai
    SUN Jian, ZHANG Ying, XUE Rui, ZHANG Yi
    China Journal of Highway and Transport. 2017, 30(5): 122-131.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To explore the formation mechanism of traffic carbon emissions under different dimensions and to clarify the main factors influencing traffic carbon emissions, multi-dimensional mobile monitoring equipment was used to construct a mobile monitoring system for urban traffic carbon emissions. Typical road networks were chosen to collect information about roads, traffic, meteorology, traffic carbon emissions and driving characteristics. At the microscopic level, Pearson correlation analysis and Granger causality test were applied to reveal that rotation rate and specific power parameter, compared with velocity and acceleration, were more relevant to vehicle carbon emissions. At the mesoscopic level, the mobile monitoring results were used to calibrate the vehicle emission model of MOVES and Cronbach's alpha coefficient was used to validate the reliability of the model. The sensitivity analysis was conducted to investigate the influence of road grade on vehicle emission factors. As it turned out, road grades significantly affected the emission factors and the average emission factor of each grade was calculated. Then, at the macroscopic level, taking the ratio of different vehicle types at different road grades into consideration, the existing vehicle emission model was revised. The results show that the total CO2, CO and HC emissions of small passenger cars in Shanghai in 2014 are 8 271.91, 76.95 and 2.13 kt, respectively. Among them, urban arterials account for 41% of the total mileage and more than 50% of the emissions. Road grade is an important influencing factor of vehicle emission factor and urban arterials. As the most important emission line source in the urban areas, urban arterials should be the key subject to implement traffic emission control strategies.
  • Cross Cameras Bicycle Re-identification for Mixed Traffic Intersections
    TAN Fei-gang, LIU Wei-ming, HUANG Ling, ZHAI Cong, ZHOU Shu-ren
    China Journal of Highway and Transport. 2017, 30(5): 132-138.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to obtain the precise dynamic track data from cross camera bicycle under the mixed traffic flow intersections, the experimental research was carried out in regard of the re-identification problem in the process of the cross camera bicycle track. The cross camera bicycle re-identification algorithm under the mixed traffic intersections based on the sample sequence grouping similarity measurement was proposed, with the considerations of complex environment of the mixed traffic intersections, illumination variation and the differences of camera view. In terms of the statistic method, the bicycle sample was divided into three parts and then the ratio of split was cumulated. Through extracting the features from the parts of bicycle gallery, corresponding prototype features were obtained by clustering analysis. With the sample sequence replacing the single sample as a probe, the quantitative analysis of samples was carried out based on comparison analysis. The feature of robustness design was analyzed and a more abstract prototype similarity feature was obtained after the similarity measurement of each sample part and its prototype. Similarity of samples was calculated by within-group linkage and no linkage between groups to improve the time complexity of algorithm by grouping sample sequence with the systematic sampling. In order to analyze the performance of the algorithm, BIKE1, the bicycle re-identification dataset was collected. Meanwhile group performance assessment, prototype parameter settings of components and similar algorithm performance comparison were experimentally compared. The results show that higher identification accuracy is gotten by regarding the sample sequence as a probe, especially when sample sequence is divided into two groups. The bicycle sample, divided into three parts, efficiently strengthens the robustness of influence of algorithm on the illumination variation. Compared with other similar algorithms, identification rate of the above algorithm is much higher.
  • Highway Value Analysis Based on Grey System Theory
    SU Jin-ling, YANG Yun-feng
    China Journal of Highway and Transport. 2017, 30(5): 139-144.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to quantify and predict the value of the highway, to measure the main factors influencing the value of the highway and to preserve or increase the value, the grey prediction method was used to establish the gray prediction model and verify its accuracy through residual test. Main factors affecting values were found to determine the relations among them based on grey correlation analysis method. Taken Fujian highway as empirical analysis object, the empirical analysis of established models was carried out. The results show that the value of Fujian highway in three years is 4.702 18 billion yuan, after passing the model accuracy test with the residual value of 0.642 0. The correlation coefficients of the net cash flows of Fujian highway values and relevant factors including the maintenance cost, operating income, collection cost, land rent, expenditure on highways, monitoring cost, and road production depreciation are 0.98, 0.94, 0.90, 0.94, 0.90, 0.87, 0.83 respectively. According to the principle of non-repetition from the high, the correlation coefficients of operating income and collection cost, road production depreciation and monitoring cost, as well as expenditure on highways and monitoring cost are 0.96, 0.94 and 0.99 respectively with high relevancy. The established model can be used for value prediction and grey correlation analysis can be used to search main factors affecting values and to determine the relation among them. The results can provide references for implementing value management of the highway.
  • Research on the Evaluation Index of Handling Stability of Tractor and Double Trailer Combination
    ZHANG Yi-hua, XU Hong-guo, LIU Hong-fei, QI Shao-sen
    China Journal of Highway and Transport. 2017, 30(5): 145-151.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to determine evaluation index of handling stability in tractor and double trailer combination and carry out the lateral stability analysis, based on analyzing research status of heavy combination abroad, effects of structural parameters, operation parameters and a variety of active control strategies on lateral stability of vehicle combination were summarized. Compared with the evaluation method of handling stability of tractor-trailer combination in China, rearward amplification (RWA) and Off-tracking of multi-articulated heavy combination were obtained. By establishing the dynamics model including yaw and lateral movement of tractor and double trailer combination, simulation of step response in each vehicle unit was completed, including variables of lateral velocity, yaw rate, lateral-yaw phase plane trajectory, lateral acceleration and articulation angle. The RWA values on the basis of yaw rate and lateral acceleration were calculated, and compared with values mentioned in relevant literatures abroad. The results show that when the maximum lateral velocities of tractor and the first trailer are 1.15 m·s-1 and 0.89 m·s-1 respectively, the maximums of corresponding dolly and the second trailer are 2.81 m·s-1 and 1.31 m·s-1 respectively, indicating that the latter is the main factor for the instability of tractor and double trailer combination. The RWA values of yaw rate and lateral acceleration are 1.14 and 1.54 respectively, with demonstrating that lateral acceleration can better reflect the state of rearward amplification. The facts that the articulation angle between tractor and the first trailer is 5.9°, the articulation angle between dolly and the second trailer is 9.6°, and the articulation angle between the first trailer and dolly restores to zero, indicate that the connection between the first trailer and dolly is more stable than that of the fifth wheel, with shorter time restoring to the steady state. The result provides a reference for the determination and application of evaluation index in handling stability of tractor and double trailer combination.
  • Improvement of Roller Running System Based on Closed-loop Control
    ZHU Wu-wei, LI Yu, FENG Zhong-xu, ZHANG Xiao-bo, YAO Yun-shi
    China Journal of Highway and Transport. 2017, 30(5): 152-158.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In order to investigate the improvement of the closed-loop control on the roller speed stability, theoretical analysis and simulation were combined to analyze the running system of the roller. The transfer function model was established by the diagram of hydraulic driving system of double-drum roller and the characteristics of hydraulic components.And transfer function relationships between the control signals and running speed response, running load and running speed response were derived. Then the traditional transfer function model of the roller running system was improved by combining closed-loop PID control characteristics, namely, proportion, integral and differentiation with the result of the present transfer function model under closed-loop control. Running tests on the 12 t double-drum roller were carried out on the basis of the theoretical derivation. After time-domain comparison and frequency-domain comparison of simulated and practical velocity curves, the simulation analysis was done to explore the effect of closed-loop PID control on the characteristics of running system. The results show that the simulation model can present the changing rule of running speed exactly under the load of fluctuation. With the PID control, the velocity stability during the roller running process is improved on the basis of invariability of the average value of the velocity. The super harmonic oscillation in the system step response has been significantly suppressed. The stability time has been improved and the response of the system is more accurate. Thus the closed-loop control applied to roller running system can improve the velocity stability under the process of smooth and steady operation of roller and the compaction quality.
News More>>
Download More>>
Links More>>
New Media
  • Wechat Account
  • WeChat video Account
Visited
    Total Visits:    Today:    Online:
Copyright © China Journal of Highway and Transport, All Rights Reserved.
Tel: 029-82334387　
E-mail：zgglxb@163.com
Powered by Beijing Magtech Co. Ltd,.