2012 Vol. 12, No. 1

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Road and railway engineering
Effect of water content on strength of unsaturated loess
LEI Sheng-you, LI Zhi-yuan, WANG Ji-qing, LIU Zhao
Abstract: Loess suction's contribution to its strength was regarded as the increment of minor principal stress.The increment was gained by analyzing the Mohr's circle geometric figure of loess ultimate stress.When loess was in ultimate state at failure, a computation method of loess strength was put forward under the condition that the cohesion and the internal friction angle synchronously changed, the relationship between the strength indexes and water content was obtained, and the relationship curves of major principal stress and water content of unsaturated loess were analyzed at failure.Computation result shows that the changing rules of computation curves and test curves for major principal stress are same, their difference becomes smaller with the increase of water content, the maximum is 11.63%, and the minimum is 1.59%, so the method is credible.With the increase of water content, when the cohesion and the internal friction angle both change, the computation value of major principal stress is larger than the value only when the cohesion changes, their relative error range is 1.26-2.17 times, which indicates that the influence of water content on the strength of unsaturated loess is significant.More>
2012, 12(1): 1-5. doi: 10.19818/j.cnki.1671-1637.2012.01.001
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Pore water pressure characteristics of semi-rigid base for cement concrete pavement
SHENG Yan-ping, CHEN Shuan-fa, WANG Dong, WANG Lin-bing
Abstract: The pore water pressure of semi-rigid base for cement concrete pavement was simulated by using finite element analysis software ABAQUS based on poroelasticity, and the distribution laws of pore water pressure along the base depth were calculated under different external loading conditions and pavement structures. Analysis result shows that in water-saturated state, pore water pressure decreases with the increase of surface thickness, surface elastic modulus, base thickness and base permeability, but increases with the increase of base elastic modulus. The elastic moduli of surface and base have no obvious impacts on pore water pressure. Meanwhile, pore water pressure linearly increases with the increase of traffic load. With the same load, denser load distribution impacts pore water pressure distribution more significantly. Loading modes only influence the dissipation of pore water pressure. With the increase of vehicle speed, pore water pressure increases, and its dissipation becomes fast.More>
2012, 12(1): 6-12. doi: 10.19818/j.cnki.1671-1637.2012.01.002
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Influence of widening modes on subgrade settlement of expressway
FAN Hong-ying, ZHE Xue-sen, BIAN Han-liang, DING Kun, ZHAO Liu-hui
Abstract: In order to research the influence of widening modes on subgrade settlement for expressway, the numerical models of subgrade settlement on the unilateral and bilateral symmetry widening modes of Xitong Expressway were set up, the change rules of top surface settlement, differential settlement and horizontal displacement of slope toe for subgrade were analyzed by using the finite element method, and the comparison result of numerical simulation values, layer-wise summation method's computation values and observation values for subgrade settlement in bilateral symmetry widening mode was analyzed.Analysis result indicates that when the widening widths are same, the decrease amplitude of settlement for old subgrade center in bilateral widening mode is 15.2% larger than the value in unilateral widening mode.The difference of subgrade settlement in widening 2 lanes on both sides is 24.3% of the value in broadening 4 lanes on one side.With the increase of widening width, the center settlement increment of old subgrade decreases gradually, and the displacement of the maximum settlement to the inside of new subgrade edge is 3-5 m.The maximum settlements from numerical simulation, layer-wise summation method and field observation are 18.40、18.74 and 16.06 mm respectively, which indicates that the numerical simulation method is reliable, and the simulation conclusion and the observation result are consistent.More>
2012, 12(1): 13-18. doi: 10.19818/j.cnki.1671-1637.2012.01.003
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Bearing capacity mechanism of non-embedded pile-plank structure subgrade
SU Qian, WANG Wu-bin, BAI Hao, LIAO Chao, ZHAO Wei
Abstract: Sensor components were disposed at the typical section of test subgrade, and the bearing capacity mechanism of non-embedded pile-plank structure in deep collapsible loess foundations was studied by long-term observation.The pile-soil interaction was considered, the concept of comprehensive rotation stiffness was introduced based on the principle of equal stiffness, the vertical and horizontal plane models of the subgrade were installed, and the deformation and mechanical characteristic of the structure were analyzed.Measured result shows that the test value of structural main reinforcement stress agree well with the theoretical calculation value, the difference is about 10%-30%, and the maximum reinforcement stress of 60.60 MPa appears at the cross section of joist.Pile side earth bears about 95% of total load, and no negative friction is produced.The load transfer law of the structure is different from that of traditional subgrade, load can be transferred to deeper bearing layer by pile foundation, which improves the stress state of soft soil section.Half a year, after the laying completion of track construction, the largest accumulated settlement of top surface for bearing plank occurs at the cross section of mid-span, which is 1.0 mm, and meets the requirement of settlement control.More>
2012, 12(1): 19-24. doi: 10.19818/j.cnki.1671-1637.2012.01.004
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Dynamic analysis of rock-fall impact on shed tunnel structure
YANG Lu, LI Shi-min, WU Zhi-min, SHEN Xin-pu
Abstract: Shed tunnel structure was taken as prototype, and the contact force, displacement, damage, and energy of shed tunnel under rock-fall impact were studied.Rock-fall was simplified to rigid sphere, surrounding rock and soil were reduced to ideal elastic materials, and concrete was regarded as elastic-plastic material.The dynamic responses of rock-fall impact on shed tunnel structure at different speeds and incident angles were simulated by using ABAQUS finite element.Analysis result shows that when incident angle is unchanged, the greater rock-fall speed is, the greater the displacement is.When rock-fall speed is constant, the smaller rock-fall incident angle is, the greater the displacement is.The worst damage of concrete protective structure occurs at rock-fall contact area, the second damages are inclined leg pillar top and beam in connection with pillar, and the intensities of pillar top and beam joint should be strengthened in practical projects.Impact energy is mainly absorbed and consumed through the concrete protective structure of shed tunnel, the absorption and consumption of soil cushion layer are very limited.To alleviate the damage of rock-fall impact on the concrete protective structure, energy shock absorber can be added at shed tunnel bearing place.More>
2012, 12(1): 25-30. doi: 10.19818/j.cnki.1671-1637.2012.01.005
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Design parameters of track-bridge interaction on passenger dedicated line cable-stayed bridge
YAN Bin, DAI Gong-lian, DONG Lin-yu
Abstract: Track-bridge interaction was simulated by using nonlinear spring, and the simulation method was proved based on the experimental results of related documents.Taking a U-shape section and single-tower cable-stayed bridge on Shanghai-Kunming Passenger Dedicated Line as an example, the spatial finite element model of tower-cable-rail-beam-pier was established by using large general-purpose finite element software ANSYS.The transfer law of rail longitudinal force on cable-stayed bridge was analyzed, and the impacts of design parameters on rail longitudinal force were studied, the design parameters included longitudinal resistance model, cable-stayed bridge structure system, temperature load, wind load and so on.Analysis result shows that rail longitudinal resistance can be simplified in accordance with ideal elastic-plastic model.Compared with floating system, rail longitudinal force reduces by about 30% through tower and beam consolidation.When calculating rail expansion force, load can be applied according to beam increasing-temperature 15 ℃ and cable increasing-temperature 40 ℃.In windy areas, rail longitudinal force on cable-stayed bridge caused by wind can be larger than 60 kN.More>
2012, 12(1): 31-37. doi: 10.19818/j.cnki.1671-1637.2012.01.006
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Transportation vehicle engineering
Extreme short-time prediction technology of high speed unmanned surface vehicle motion
MA Wei-jia, SHI Sheng-zhe, ZOU Jing, PANG Yong-jie, ZHU Kai
Abstract: Multiple seasonal ARIMA(auto regressive integrated moving average) model based on time series was used, the extreme short-time prediction technology of unmanned surface vehicle motion was studied based on the seakeeping test data of boat model in regular wave.ARMA(auto regressive moving average) models with trend difference and seasonal difference were adopted, Akaike information criterion and white noise inspection method were carried out, and the chosen best model was validated.Extreme short-time prediction in twenty steps was made for unmanned surface vehicle.Calculation result indicates that the maximum errors are not more than 6% in the former ten-step predictions of acceleration, heave and pitch.With the increase of prediction step, the error has enlarging trend, the maximum error reaches to 16.68% in the following ten-step prediction of acceleration.So extreme short-time prediction technology is effective.More>
2012, 12(1): 38-44. doi: 10.19818/j.cnki.1671-1637.2012.01.007
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Safety analysis of aircraft encountering wake vortex
HAN Hong-rong, LI Na, WEI Zhi-qiang
Abstract: The response mechanism of aircraft encountering wake vortex was analyzed, and the calculation model of induced moment was developed. The calculating model of aircraft's rolling parameters was constructed based on considering of the damping characteristics of aircraft, the response times, the handling qualities and so on. The calculation model of the accepted maximum bank angle was constructed based on the assumption that the buffet stall speed was posed as a critical limit in calculating the rolling progress. The rolling parameters and safe intervals of wake vortex under certain wake vortex's field condition were calculated by using DelphiT. 0. The influences of aircraft mass, speed, altitude tolerance and initial bank angle on flight safety were analyzed. Research result shows that at a certain speed, the greater aircraft mass is, the smaller the accepted maximum bank angle is. The safe interval of aircraft with certain mass decreases with the increase of speed and the decrease of altitude tolerance, while it increases with the increase of initial bank angle. Comparing the data calculated by the models with ICAO standard data, the maximal deviation is 1.56%, which verifies the correctness of the computation method.More>
2012, 12(1): 45-49. doi: 10.19818/j.cnki.1671-1637.2012.01.008
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Calculation model of automobile braking distance on pavement with deicing salt
LI Zhi-peng, PENG Tao, WANG Qian, ZHAN Zhang-shu
Abstract: The forces conditions of front and rear wheels during automobile braking process were analyzed, and a mathematical model of automobile braking distance and road adhesion coefficient was established.Braking tests on ice-snow-covered pavement and the pavement after using deicing salt were carried out, and the braking distances under different primary braking speeds were calculated by using MATLAB software.Test result shows that on ice-snow-covered pavement, when the primary braking speeds are 10.8, 24.4, 31.4 km·h-1 respectively, the braking distances are 2.959, 18.378, 26.264 m respectively.On the pavement after using deicing salt, when the primary braking speeds are 11.0, 22.9, 31.0 km·h-1 respectively, the braking distances are 2.430, 13.766, 18.860 m respectively.After using deicing salt, the adhesion coefficient of the pavement increases significantly, and the test braking distance decreases by 25%-28%, the simulation braking distance decreases by about 30% and is close to the test value.So the calculation model is feasible.More>
2012, 12(1): 50-54. doi: 10.19818/j.cnki.1671-1637.2012.01.009
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Transportation planning and management
Following distance model of inland ship
HE Liang-de, JIANG Ye, YIN Zhao-jin, ZHOU Bo, TANG Hui
Abstract: In order to study the characteristics of inland ship flow, the correlation among breaking distance, ship length and speed was analyzed, the empirical equation of breaking distance was given based on ship breaking mechanism.The impact of operator experience on actual breaking distance was considered, and the following distance model of inland ship was established.Combined with instance analysis including single motorship, pushing fleet and towing fleet in Jiangsu, the parameters of following distance model were determined by analyzing the empirical value of major axis for inland ship domain and the computing value of piecewise linear model of 100 t single motorship.Analysis result shows that the breaking distances of 3 ship categories are related to the lengths of single ship, fleet and the longest barge, and the calculated length coefficients are 5.98, 2.73 and 17.41 respectively.The breaking distances of single motorship and pushing fleet are in direct proportion to the square of ship speed, the breaking distance of towing fleet is in direct proportion to the 0.85 th power of ship speed.The breaking operation coefficient and index of ship operator are determined as 0.78 and 2.5 respectively.More>
2012, 12(1): 55-62. doi: 10.19818/j.cnki.1671-1637.2012.01.010
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Relation between accident rate and horizontal alignment for mountain highway
GUO Ying-shi, FU Rui, YUAN Wei, LI Yu-liang, MA Yong, WANG Chang
Abstract: The traffic accident data and horizontal alignment data of two mountain highways were collected, the curvature change rate was regarded as the characteristic parameter of horizontal alignment, the regression analysis between accident rate and curvature change rate on current sample section was carried out, and the average curvature change rates of those several calculation intervals were respectively calculated, which were 0.25, 0.50, 0.75, 1.00 and 1.50 km upward of current sample section.The secondary treatment on the curvature change rate was carried out, and the relations between the accident rates and the curvature change rates were fitted by using least square method.Analysis result shows that the fitting determination coefficients between the accident rates and the curvature change rates on sections 1 and 2 are lower, are about 0.414 2 and 0.120 8 respectively.While on the calculation intervals that are 0.5 km upward of current sample sections, their positively secondary parabolic relations both are the most significantly, and the fitting determination coefficients are 0.966 1 and 0.790 8 respectively.While the average curvature change rate is about 0.002 0(°)·km-1, the accident rate is lowest.More>
2012, 12(1): 63-71. doi: 10.19818/j.cnki.1671-1637.2012.01.011
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Quantitative evaluation method of vehicle emission in urban region
GUO Dong, GAO Song, ZOU Guang-de, TAN De-rong, WANG Xiao-yuan, SHAO Jin-ju
Abstract: The on-board emission test platform of vehicles was put up, and the actual emission data were obtained.The specific power divisions of light-duty vehicles were carried out, and the quality emission ratios of three emission pollutants were gotten.Based on OD data back-stepping, speed and acceleration were taken as input parameters, and the total emissions and emission ratios of vehicles in urban region were calculated by using emission model and traffic simulation model.Calculation result indicates that during late-peak period, the hour emissions of CO, HC and NOx are 163.364 7, 19.453 9 and 77.701 8 kg respectively.CO emission ratios of light-duty vehicles, middle-duty vehicles and busses are 65.45%, 29.57% and 4.98% respectively.HC emission ratios of light-duty vehicles, middle-duty vehicles and busses are 57.68%, 26.03% and 16.29% respectively.NOx emission ratios of light-duty vehicles, middle-duty vehicles and busses are 48.11%, 4.63% and 47.26% respectively.Light-duty and medium-duty vehicles are the emission control emphases of CO and HC, and busses are the emission control emphasis of NOx.More>
2012, 12(1): 72-78. doi: 10.19818/j.cnki.1671-1637.2012.01.012
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Traffic impact post-evaluation model of urban construction project
HUO Ya-min, CHEN Jian, LI Xiao-hu, YANG Fei
Abstract: Based on the post-evaluation principle, a traffic impact post-evaluation(TIPE) model of urban construction project was set up, its indexes were selected by using the method of weight judgment.The weight of each index was determined by using the frame weight method of single criterion AHP, and each index was normalized by calculating deviation rate.In the three-grade evaluation index system of TIPE, the first-grade indexes are traffic demand prediction post-evaluation index, traffic improvement measure post-evaluation index and traffic sustainability post-evaluation index respectively.The second-grade indexes are background traffic demand prediction index, project traffic demand prediction index, regional traffic demand prediction index, public transportation demand prediction index, static traffic demand prediction index, land use improvement index, improvement measure index of traffic organization, traffic adaptability index, economic impact index, environmental impact index and social impact index respectively.The TIPE result of Boyuan Garden in Chengdu City indicates that the maximal membership degree is 0.527 7, the evaluation grade is partly successful, and the result is practical.So, the evaluation index system and model are effective.More>
2012, 12(1): 79-86. doi: 10.19818/j.cnki.1671-1637.2012.01.013
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Intrinsic influence mechanisms of dry bulk ship investment and ordering
ZHENG Shi-yuan
Abstract: The intrinsic influence mechanisms of dry bulk ship ordering were studied by using the theory and approach of dynamic econometrics. The dynamic relationships among new ship prices, second-hand ship prices, time charter rates and ordering volumes of three main kinds of dry bulk ships were analyzed. Analysis result shows that there are no cointegration relationships among new ship prices and second-hand ship prices for three kinds of dry bulk ships, and there are cointegration relationships among new ship price, second-hand ship price, time charter rate and ordering volume for every kind of dry bulk ship. Ship ordering volume has positive relationship with new ship price, and negative relationship with time charter rate. The relationship between second-hand ship price and ship ordering volume for Capsize ship is positive, it is negative for Panamax ship, and it is not significant for Handymax ship. Impulses from time charter rates to ship ordering volume are the biggest for three kinds of ships. Impulse from new ship price to ship ordering volume for Handymax ship is the smallest among three kinds of ships. Impulse from second-hand ship price to ship ordering volume for Panamax ship is positive, while it is negative for Capsize ship or Handymax ship.More>
2012, 12(1): 87-94. doi: 10.19818/j.cnki.1671-1637.2012.01.014
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Transfer payment mode of financial fund for rural highway
LI Li, LIU Yan-na, XU Xing
Abstract: The defects of current transfer payment mode of financial fund for rural highway were analyzed.The efficiency and the equality were taken as principles, the transportation demand and the financial ability were taken as objectives, and a new transfer payment mode was put out.The transportation demand and the standard traffic volume were confirmed, and the investment amount of rural highway was calculated.Based on the payment proportion of the higher government and the lower government and the financial ability of local government, the transfer payment amount of financial fund for rural highway was finally confirmed, and the differences of the two modes were compared by using the data of 11 country towns in Xianyang City obtained by using statistical analysis software SPSS.Research result shows that the correlation coefficients of subsidy amount rankings and financial ability rankings for the two modes are-0.755 and 0.309 respectively, and their saliencies are 0.007 and 0.355 respectively.When the relative approach degree of the two rankings is calculated by using the current mode, 2 values are 0.50, 4 values belong to [0.20, 0.30), and 5 values are all less than 0.20.While 2 values of the relative approach degree computed by using the new mode are infinite, 2 values are 1.00, 2 values are 0.50, 5 values belong to [0.20, 0.30), and only 1 value is less than 0.20.Obviously, the new mode is rational and is consideration to efficiency and equality.More>
2012, 12(1): 95-101. doi: 10.19818/j.cnki.1671-1637.2012.01.015
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Traffic information engineering and control
Speed guidance predictive control model on urban expressway
CHEN Da-shan, SUN Jian, LI Ke-ping
Abstract: In the control system of urban expressway, speed guidance was taken as control variable, and the macro dynamic traffic flow of urban experssway model was established. Total vehicle traveling time and speed guidance were taken as objective functions, and the entrance flows of urban expressway and ramp were calculated. The speed guidance predictive control model of urban expressway was established to optimize speed guidance, and the mutation of downstream traffic flow was simulated by using MATLAB. Simulation result shows that because of speed guidance control, the average speed of traffic flow increases from 72. 704 6 km~ h-1 to 74. 167 6 km ~ h-1, the average density of traffic flow decreases from 23. 011 2 veh ~ km-1 to 21. 156 7 veh ~ km-1, and their fluctuations are less than 8%. The speed variance of traffic flow decreases, and the maximum value is only 420 (kin ~ h-1)2. The speed and density deviation ratios between before and after speed guidance control are 3.57 and 1.91 respectively. During traffic flow's mutation period, the speed and density deviation ratios between before and after speed guidance control are 4. 56 and 2. 34 respectively. So the control model is effective.More>
2012, 12(1): 102-107. doi: 10.19818/j.cnki.1671-1637.2012.01.016
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Optimization algorithm of train operation energy consumption based on genetic algorithm
CHEN Rong-wu, LIU Li, GUO Jin
Abstract: Train control model and train operation regulation in communication based train control(CBTC) system were studied, train operation control in inter-station section was optimized combinatorially for the purpose of reducing energy consumption, and the optimization algorithm of train operation energy consumption based on genetic algorithm was provided.Train operation speed curves were calculated for each performance level or specified run time of each section under particular line conditions.Energy consumption calculation and optimization simulation were performed on a 2 400-meter long track line with the setting of a typical energy saving grade and a 60 km·h-1 speed restriction area.Analysis result shows that the traction energy consumptions of optimized speed curve reduce to 62%, 58%, 60% of speed curves for performance levels 2, 3, 4 respectively, energy saving effect is remarkable, and the optimization algorithm is efficient.More>
2012, 12(1): 108-114. doi: 10.19818/j.cnki.1671-1637.2012.01.017
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Conflict resolution model of optimal flight for fixation airway
HAN Yun-xiang, TANG Xin-min, HAN Song-chen
Abstract: Aiming at the conflict resolution problem among several aircrafts under fixation airway, the flight strategy of changing course was proposed, and the optimal conflict resolution models under free flight and fixation airway were compared. Aircraft performance and airway space were taken as constraint conditions, the conflict resolution time was taken as objective function, optimal control theory and differential equation were used, and the total conflict resolution times under different initial conditions were computed. Computation result shows that while the resolution endpoint of aircraft changes from (80, 0) to (65, 0), the total conflict resolution time reduces 32 s. While the resolution speed of aircraft decreases from 833 km·h-1 to 759 km·h-1, the total conflict resolution time increases 12 s. While the initial position of aircraft increaes from (20, 0) to (29, 0), the total conflict resolution time only increases 2 s. The resolution endpoint and resolution speed of aircraft have great influence on the conflict resolution time, but the initial position of aircraft has little influence on the conflict resolution time.More>
2012, 12(1): 115-120. doi: 10.19818/j.cnki.1671-1637.2012.01.018
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Inductive benefit simulation algorithm of VMS travel time
GAN Hong-cheng, YANG Zhen-zhen
Abstract: Based on macroscopic traffic simulation model, the inductive benefit simulation method of variable message sign(VMS) travel time was proposed, and the influences of information concern ratio and information comprehension deviation coefficients for drivers on the inductive benefit of VMS travel time were analyzed. The travel time calculation model, driver information response model and METANET simulation model were taken as theory foundations, the improving ratio of total road network consuming time was taken as inductive benefit objective, and simulation tests on three road networks with different sizes were carried out. Simulation result shows that VMS travel time normally has positive inductive benefit on improving the running efficiency of road network. The higher the information concern ratio is, the smaller the information comprehension deviation coefficient is, and the more significant the inductive benefit is. While information concern ratio is over 80G, the inductive benefits of small, medium and large road networks are above 28. 89%, 15. 87% and 10. 53% respectively. So the simulation algorithm is effective.More>
2012, 12(1): 121-126. doi: 10.19818/j.cnki.1671-1637.2012.01.019
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