2015 Vol. 15, No. 3

Display Method:
Study on test standard of asphalt mixture dynamic modulus
XU Zhi-rong, CHANG Yan-ting, CHEN Zhong-da, SUN Jian, LIU Yun
Abstract: Based on the foreign research achievements and experience, the dynamic modulus of asphalt mixture was measured by using unconfined compressive strength test method. The uneven distributions of static pressing specimens were verified, the making method of specimens was improved, and the cutting static pressing specimens were obtained. The porosities of 2 kinds of specimens were compared. According to Vander Poel formulas, load frequency was determined. The clearance loading mode was used, and the load cycle was determined based on the principle of specimens reaching steady vibration state. Dynamic modulus was calculated according to the average peak strains of last 5 load cycles. The load levels and strain measurement methods were determined, and the test data at stable phase were selected as the final test results. The dynamic moduli of cutting static pressing specimens were tested, and the mean value, mean square deviation and variation coefficient of dynamic moduli were calculated. Analysis result indicates that the average porosity of cutting static pressing specimens is 4.2%, and is far less than the average porosity of static pressing specimens, which is 6.5%. The discrete of cutting static pressing specimens is small, and the void distribution is uniform. Compared with static pressing specimens, the porosities of cutting specimens are closer to Marshall specimens, and the cutting specimens are easier to reach steady vibration state under loading. Haversine wave, load frequency of 10 Hz, load clearance time of 0.9 s and load level of 0.7 MPa are closer to the roles of traffic loads. The top surface method is used to measure the deformation of specimens. The specimens have reached steady vibration state when the load cycles is 200 times, so the load cycles is determined as 200 times. For a single specimen, the test data of 3-5 load cycles are selected to calculate dynamic modulus. When the difference between the dynamic modulus of 3 and 5 load cycles is no less than 200 MPa, the specimens should be discarded. The dynamic moduli of the 3 kinds of asphalt mixtures are 1 650-2 970 MPa, and the discrete is small. The mean square deviations of dynamic moduli are 100-230 MPa, the variation coefficients of dynamic moduli are 5%-9%, so the method is feasible.More>
2015, 15(3): 1-8. doi: 10.19818/j.cnki.1671-1637.2015.03.001
Calculation method of composite foundation settlement under high-speed railway subgrade
LEI Sheng-you, LI Xiao-lun, LI Yang, LI Meng-sha, HUI Hui-qing
Abstract: Boussinesq combination method, Boussinesq direct method, Boussinesq triangular method and German DB836 method were applied to calculate the foundation additional stress. Composite modulus, modulus calculated by bearing capacity ratio method, and chord modulus were applied as foundation modulus respectively. 12 combining forms were used to calculate the total foundation settlement, and the calculated results were compared with the measured settlements of test sections of high-speed railway. Calculation result shows that when foundation additional stress is calculated by Boussinesq combination method, Boussinesq direct method and German DB836 method, and foundation modulus is chord modulus calculated by composite foundation load plate test, the calculated total foundation settlements are very close to the measured value, and the relative differences are 1.57-9.81%, which can meet the requirement of foundation settlement control for high-speed railway. Therefore, it is recommended to apply additional stress-modulus method to calculate the foundation settlement of subgrade construction for high-speed railway, in which the foundation addition stress can be calculated by Boussinesq combination method, Boussinesq direct method and German DB836 method, and chord modulus is applied as foundation modulus.More>
2015, 15(3): 9-15. doi: 10.19818/j.cnki.1671-1637.2015.03.002
Influence of pile-raft foundation reinforcement on subgrade of adjacent existing railway
LIU Wei-zheng, XU Lin-rong, ZUO Shen, LIU Zhang-hong, CHEN Peng-fei
Abstract: During the process of pile-raft foundation reinforcement of new railway, the deformation and stress of subgrade for adjacent existing railway were measured in situ by using stress spade, horizontal strain gauge and inclinometer, and the mechanical characteristics and deformation laws of subgrade were analyzed. In order to minimize test error, a finite element model (FEM) was built to calculate the subgrade deformation and stability, the conversion factor of slope horizontal displacement was obtained, and the maximum shear stress and slope safety factors of subgrade under different excavation depths were calculated using the FEM. Based on the monitoring and calculated results, the optimized protection measures were proposed and applied during the construction process, such as pile-raft interval construction, changing pile eonstruction, and hunging mesh with steel band and grouting along the subgrade slope. The protection effect was verified with the data from track inspection car by using scoring method and standard difference method. Analysis result indicates that the cumulative slope horizontal displacement of slope foot for adjacent existing railway is 24.25 mm during construction process, and the lateral displacement per day is less than 0. 59 mm. The horizontal displacement is sensitive to the construction process and can be used as a key indicator to describe the stability of subgrade. The horizontal stress of foundation soil in the depth range from 0 to 9 m between the new railway and existing railway increases and then decreases, the compressive stress is less than 10 kPa and the stress level does not change significantly in different construction stages. The safety factor of slope decreases from 1.08 to 0.54 as the excavation depth reach 2.2 m under the soak condition, and then the state of subgrade is unstable failure, the protection measures must be adopted in the subgrade slope. The track quality index(TQI) of the existing line increases by 129.58~during the construction process, which indicates the large linear fluctuation of geometry for existing railway, but the TQI is less than its safety limit, which indicates that the deformation of subgrade is controlled effectively by using optimized protection measures.More>
2015, 15(3): 16-26. doi: 10.19818/j.cnki.1671-1637.2015.03.003
Influence of intermediate principal stress coefficient on character of soft clay under rotation of principal stress axes
LIU Yan-hua, XIE Yong-li
Abstract: A series of undrained shear tests were carried out on Shanghai undisturbed soft clay by using hollow cylinder apparatus.Under the rotation of principal stress axes, the influence of intermediate principal stress coefficient on the deformation and strength character of saturated soft clay was researched.The hollow thin-walled samples of soft clay were consolidated under isotropic consolidation modes.Under 3 kinds of rotation angles of principal stress axes, a series of undrained shear tests were carried out with different intermediate principal stress coefficients.During the shear tests, the deviator stress increased until the sample was destroyed, while average stress, intermediate principal stress coefficient and the rotation angle of principal stress axes remained unchanged.Test result indicates that the deformation behavior and strength character of natural soft clay were obviously different under different intermediate principal stress coefficients.The critical stress ratio and undrained shear strength decrease with the increase of intermediate principal stress coefficient under the three kinds of rotation angles of principal stress axes.When the rotation angle of principal stress axes is 0°, the shear stresses of samples with the intermediate principal stress coefficients of 0.25 and 0.50 decrease after arriving the peak values because of slight strain localization.When the rotation angle of principal stress axes is 90°, and intermediate principal stress coefficients are 0.50 and 0.75, the peak values of shear strength are similar, and the sample states are non-axisymmetrical tensile with unequal inner and outer pressure.Moreover, when the intermediate principal stress coefficient is 1.00, comparing with the coefficients of 0.50 and 0.75, the peak shear strength decreases by 25%, and the sample states are axisymmetrical tensile with equal inner and outer pressure.If the equal internal and external pressures are applied, when the rotation angle of principal stress axes increase from 0° to 90°, the intermediate principal stress coefficient increase from 0 to 1.00, and the critical stress ratio of samples and undrained shear strength decrease.More>
2015, 15(3): 27-33. doi: 10.19818/j.cnki.1671-1637.2015.03.004
Diagnostic model of crack for tunnel lining based on gray and catastrophe theories
ZHANG Su-lei, CHEN Huai, WANG Ya-qiong
Abstract: In order to evaluate the stability of crack for tunnel lining by using finite monitoring data, wavelet transform was applied to analyze the monitoring data of cracks for tunnel lining, the high frequency part caused by environmental change and test error was eliminated, and the low frequency part caused by surrounding rock pressure variation was kept, thus, the time- dependent deformation of lining crack was decomposed. The GM (1, 1) gray prediction model of time-dependent deformation of lining crack was built based on gray theory to predict the later development of lining crack by using early monitoring data. The stability criterion of lining crack was established based on the equilibrium conditions of cusp catastrophe model. The diagnostic model of lining crack was established based on gray and catastrophe theories, and two typical lining cracks were analyzed based on the model. Analysis result indicates that the stability criterion values of two cracks are larger than 0, so, they do not meet the instability condition. The measured variations of crack widths are less than O. 2 mm, the variation rates are less than O. 002 mm· d-1, which shows that two cracks are basically stable. Obviously, this diagnostic model can predict the development tendency of lining cracks correctly.More>
2015, 15(3): 34-40. doi: 10.19818/j.cnki.1671-1637.2015.03.005
Mechanical characteristic test of tunnel support structure in weak loess stratum
LAI Jin-xing, WANG Kai-yun, LAI Hong-peng, QIU Jun-ling, XIE Yong-li
Abstract: In order to analyze the mechanical characteristics of tunnel support structure in weak loess stratum and optimize the design theory of loess tunnel, large scale field tests of the sections of miscellaneous fill, deep depth and shallow depth were conducted for a loess tunnel of the highway through Xining City. In the aspects of space distribution, time distribution, calculation method and contrast verification, the contact pressure between surrounding rock and primary liner, the contact pressure between primary liner and secondary liner, and the strains of secondary liner and inverted arch were systematically studied. Analysis result shows that the vault and spandrel are the most dangerous parts of loess tunnel for their large pressures and prone to collapse. The calculated values of surrounding rock pressure are very different from the measured values, and the existing method has a big error in the calculation of surrounding rock pressure at the loess section. The time for surrounding rock pressure to stabilize is shorter at deep depth section than the value at shallow depth section, and the time at the section of miscellaneous fill is the longest. Following the guidance of New Austrian Tunnelling Method for the loess tunnel and the design concept of "strong primary liner and weak secondary liner", the loading proportions of the secondary liner have been kept in the range of 11%-36% and the primary liner has played an important role in controlling the deformation of surrounding rock. The secondary liner has played as safety reserve.More>
2015, 15(3): 41-51. doi: 10.19818/j.cnki.1671-1637.2015.03.006
Mechanical properties of ten thousand-ton class cable-stayed bridge in rotation construction process
WANG Li-feng, WANG Er-qiang, SUN Yong-cun, HE Dong-po, GE Jun-ying
Abstract: In order to reveal the mechanical properties of each component of cable-stayed bridge in rotation construction process, the 3D numerical simulation model of the first domestic single-point flat-hinge cable-stayed bridge of China was built, and was verified by using the measured data. The angular acceleration of cable-stayed bridge in rotation construction process was deduced according to the theory of rigid body rotation around a fixed axle. In view of two typical construction stages of accelerating rotation and uniform rotation, the stress states of main girder, tower, pier, bracket, shaft and dial were researched. In the rotation process of cable-stayed bridge, the influence laws of angular velocity and angular acceleration on bridge stress were revealed, and the reasonable construction angular velocity and angular acceleration were calculated. Calculation result indicates that in the process of uniform rotation, the normal stress change of control section is approximately direct proportional to the square of angular velocity. When the measured angular velocity is 0.01 rad · min-1, the maximum stress changing value of control section is only -2.00 Pa. In the process of accelerating rotation, the stress of main girder cross section presents skew symmetric distribution along the center line of main girder, and when the measured angular acceleration is 6.5 × 10-3 rad · s-2, the stress changing value of tower root solid section at lower edge is -3.33 MPa, and the stress changes significantly. In the process of accelerating rotation, start from the bracket bottom, the torque of each pier cross section along the height direction decreases. So in the process of uniform rotation, the influence of angular velocity on the stress of main girder section may be ignored. In the process of accelerating rotation, in order to ensure the construction safety and shorten the rotation time, the rotation angular acceleration of cable-stayed bridge should be limited.More>
2015, 15(3): 52-61. doi: 10.19818/j.cnki.1671-1637.2015.03.007
Inertia effects of cutting energy absorption
LIU Guo-wei, XIA Qian, WANG Qian-ye, DONG Ru-ling
Abstract: Based on considering the influence of cutting heat, the inertia effects of cutting energy absorption were studied by numerical simulation, and stable cutting force, cutting displacement, maximum temperature, heat dissipative energy and the dissipative proportion of thermal energy were computed under different initial impact conditions.Computation result shows when the initial impact energy is 20 kJ and there are no distinct initial cutting force peaks in chip formation, the stable cutting force ranges from 63.0 kN to 63.8 kN, and the changing rules and trends of cutting force curves are approximately same.When the impact mass is 200 kg and the impact velocity changes from 3 m·s-1 to 10 m·s-1, the stable cutting force ranges from 63.0 kN to 64.4 k N.When the impact velocity is 10 m·s-1 and the impact mass changes from 0.4 t to 3.2 t, the heat dissipative energy increases from 4.12 kJ to 36.64 kJ, the maximum temperature changes between 586 ℃ and 602 ℃, the dissipative proportion of thermal energy ranges from 20.6% to 23.2%, and the stable force ranges from 63.0 kN to 64.1 kN. Obviously, when the cutting depth and the geometrical parameters of cutting tool are defined, the initial impact energy, impact mass and impact velocity have little effect on the cutting force, the inertia effects of cutting energy-absorbing process are insensitive, and the cutting energy-absorbing structure belongs to type Ⅰ.The cutting heat accounts for a large proportion of energy dissipation and is greatly influenced by the initial impact velocity.More>
2015, 15(3): 62-70. doi: 10.19818/j.cnki.1671-1637.2015.03.008
Vertical rotating behavior of coupler for multiple units to multiple units rescue under braking conditions
WEI Lai, ZENG Jing, CHEN Kai, WANG Qun-sheng, GAO Hao
Abstract: In order to study the braking-induced impact for multiple units(MU)to multiple units rescue, the different configuration types of MU dynamics models were built. Actual kinematic relations and hysteresis characteristics were considered in the established coupler/draft gear dynamics model. The threshold values of coupled rescue MU for running safety were formulated. The dynamics response of MU and coupler/draft gear system under emergency braking were analyzed. The dynamics rotational behavior of coupler on the straight line and the influences of MU configurations, braking decelerations and coupler free-rotation angles on MU running safety were studied. Computation result shows that in the rescue scene of MU A to MU B, the longitudinal compressed force of coupler and the vertical rotating angle of coupler reach 799.4 kN and 11.5°, respectively, and the subjected vertical force of front supporting beam and the vertical relative displacement between adjacent carbodies reach 136.2 kN and 126.2 mm, respectively, which exceed the limit values, 80 kN and 95 mm, respectively. The vertical force components lead to carbody pitch and wheel unloading, which results in the local structural damages and the MU motion interference. The subjected vertical force of front supporting beam is lower than the limit value when the braking level decreases to No.7 level or the free pitch angle of coupler decreases to 4°, but the vertical relative displacement between adjacent carbodies exceeds the limit value. The vertical relative displacement is lower than the limit value when the braking level decreases to No.6 level or the free pitch angle of coupler decreases to 2°. 2 tabs, 11 figs, 20 refs.More>
2015, 15(3): 71-77.
Monitoring method of vehicle axle temperature based on dynamic time warping
CAO Yuan, WANG Yu-jue, MA Lian-chuan, CHEN Lei
Abstract: In order to handle with the abnormal data of vehicle axle temperature, such as jump, deletion and noise, a monitoring method of vehicle axle temperature based on dynamic time warping method was put forward to reduce the false alarm rate. The historical monitoring data and historical statistical data were preprocessed by using exponential smoothing method. At the training stage, the data were iterated to get the reference samples of different axle temperature modes. The frame matching distance matrix was obtained by computing Euclidean distances of data frames between real-time axle temperatures and reference samples. With the idea of dynamic programming and backtracking, the cumulative distance matrix and dynamic time warping path were calculated. The dynamic time warping distance was taken as the quantitative similarity index of two time series to the corresponding axle temperature mode for the minimum dynamic time warping distance, thus the axle temperature condition was achieved. Simulation result shows that when 1 000 test samples of axle temperature with the time ranges of 50 min to 300 min are inputted in MATLAB, the maximum response time is less than 0.4 s, there are 29 false matches, and the false alarm rate is below 3~. The jump interferences of axle temperature are effectively eliminated by processing the data using exponential smoothing method. The values and numbers of axle temperature jumps are different, but the relative dynamic time warping distances are invariable. Obviously, the method can meet the real-time and accuracy requirements of vehicle axle temperature monitoring and reduces the false alarm rate.More>
2015, 15(3): 78-84, 100. doi: 10.19818/j.cnki.1671-1637.2015.03.009
Importance measure of aircraft anti-icing cavity stucture parameters
ZHANG Feng, YAO Hui-ju, NAN Hua, LU: Cheng-cheng
Abstract: The three common aircraft anti-icing cavity structures were analyzed, the grid model of anti-icing cavity structure with double skins was set up by using Gambit software. The flowing condition of heat in anti-icing cavity structure was simulated by using Spalart-Allmaras turbulence model, the heat transfer efficiency was analyzed with Fluent software, and the importance measure model of anti-icing cavity structure on heat transfer efficiency was built. The function relationship between structure parameters and heat transfer coefficient for anti-icing cavity was established by using the stochastic response surface method, the low dispersion sampling method was used to solve the importance measure, and the analysis process of importance measure for anti-icing cavity structure parameters was set up. Analysis result shows that when the distance between piccolo tube center and outer skin increases from 35.15 mm to 38.85 mm, the heat transfer coefficient reduces from 0. 505 to 0. 463. When the channel height of double skins increases from 2.85 mm to 3. 15 mm, the heat transfer coefficient reduces from 0. 495 to 0. 476. When the jet hole diameter increases from 1.90 mm to 2.10 mm, the heat transfer coefficient reduces from 0. 505 to 0. 494. When the jet hole angle increases from 14. 25~ to 15.75~, the heat transfer coefficient increases from 0. 476 to 0. 494. The importance order of anti-icing cavity parameters is the jet hole angle, the distance between piccolo tube center and outer skin, the jet hole diameter, the channel height of double skins. In the machining and assembly process of anti- icing cavity structure, the jet hole angle and the distance between piccolo tube center and outer skin are mainly considered.More>
2015, 15(3): 85-91. doi: 10.19818/j.cnki.1671-1637.2015.03.010
Prediction method of aero-engine life on wing based on LS-SVM algorithm and performance reliability
MA Xiao-jun, REN Shu-hong, ZUO Hong-fu, WEN Zhen-hua
Abstract: Based on the monitoring data of practical performance for aero-engine, the degradation model of time-varying performance was established, and the performance trend was predicted. According to the much information related to aero-engine life on wing in the monitoring data, the relation between the performance degradation process and the failure distribution function was analyzed, and the aero-engine life on wing under a given reliability was obtained. Based on the practical life data on wing for aero-engine, the distribution model of life on wing was tested by using K-S fitting test method, and the model parameters was determined by using least squares- support vector machine (LS-SVM). Combined with the performance degradation trend, the revised life on wing for aero-engine was calculated, and example verification on six PW4000 aero-engines was carried out. Analysis result shows that when regularization parameters are 25, 37, 28, 40, 27 and 35 respectively, the practical lives on wing for six PW4000 aero-engines are 6 921, 7 160, 7 820, 8 490, 8 498, 6 921 cycles in order, while the corresponding prediction values are 6 534, 6 726, 7 378, 7 940, 9 103, 6 534 cycles in order. The maximum relative error is 0. 071 190, the minimum relative error is 0. 055 917, and the mean relative error is 0.060 824. The practical engineering requirement can be commendably satisfied by using the proposed method.More>
2015, 15(3): 92-100. doi: 10.19818/j.cnki.1671-1637.2015.03.011
Setting method of raised pavement marker interval at line section of freeway
LIANG Guo-hua, YAO Guang-peng, LI Kai-lun, DENG Han-yue, LIANG Kang, WANG Yu-chen
Abstract: Based on the driver's visual inertia, visual warning frequency and feeling feature, the visual warning effect of raised pavement marker was analyzed, the flash frequency of raised pavement marker was determined, and the initial interval of raised pavement marker was calculated and corrected. By using the simulation software module ADAMS/Car, the simulation models of road, vehicle and raised pavement marker were built, vehicle type was set as truck and car, the speed of truck was set as 60, 80, 100 km· h-1 respectively, the speed of car was set as 80, 100, 120 km · h-1 respectively, and the steering wheel angles of truck and car were set as 1°, 3°, 5° respectively. The simulation times were 243 for the calculated 12 m-interval and 15 m- interval recommended in the current specification respectively, and the warning effect was analyzed. Simulation result shows that under the 12 m-interval condition, the average crushing rate is 93.1%, and the average warning rates for ear and truck are 41.7% and 5.6% respectively. Under the 15 m-interval condition, the average crushing rate is 9a. 7%, and the average warning rates for car and truck are33.3% and 28. 9% respectively. Both two intervals have good vibration warning effect on cars, 15 m-interval has a better vibration warning effect on trucks than 12 m-interval. When there is a great traffic flow at night or the safe effect of traffic equipment need to be enhanced at night, 12 m-interval can be chosen to provide a good visual continuity and visual warning effect. When the convenience and economy of construction and maintenance are considered or there is a higher percentage of trucks in traffic flow, 15 m-interval can be chosen.More>
2015, 15(3): 101-108. doi: 10.19818/j.cnki.1671-1637.2015.03.012
Driving safety analysis of semi-trailer train at circular curve section in mountain area
JIANG Kang, ZHANG Meng-ya, CHEN Yi-kai
Abstract: According to the characteristics of circular curve section for mountain area, the stress and deformation conditions of tire were analyzed, and the dynamics coupling model of semi-trailer train and the circular curve section in mountain area was established. The tire slip angles and articulation angle of tractor and semi-trailer were taken as indexes, the influences of the radius, superelevation and sliding adhesion coefficient of circular curve section on the driving safety of semi-trailer train under various speeds were analyzed by using the proposed dynamics simulation method, and the calculation results among running speed method, theoretic limit speed method and dynamics simulation method were compared. Simulation result shows that when the circular curve radius is 125 m, the superelevation is 2 %, the sliding adhesion coefficients are 0. 20, 0. 35, 0. 50 and 0.80 respectively, the critical safe speeds are 20, 35, 55, 72 km · h-1 by using dynamics simulation method, all the critical safe speeds are 50 km · h-1 by using running speed method, and the critical safe speeds are 20, 35, 55, 72 km· h-1 by using theoretic limit speed method respectively. When the circular curve radius is 250 m, the sliding adhesion coefficient is 0. 35, the superelevation are O, 2%, 40/40 and 6% respectively, the critical safe speeds are 35, 38, 25, 20 km · h-1 by using dynamics simulation method respectively, all the critical safe speeds are 60 km · h-1 by using running speed method, and the critical safe speeds are 30, 31, 32, 33 km · h-1 by using theoretic limit speed method respectively. When the superelevation is 6%, the sliding adhesion coefficient is O. 50, the circular curve radii are 125, 250, 400, 650 m respectively, the critical safe speeds are 58, 62, 70, 72 km ~ h-~ by using dynamics simulation method respectively, the critical safe speeds are 50, 60, 68, 71 km ·h-1 by using running speed method respectively, and the critical safe speeds are 28, 37, 48, 60 km · h-1 by using theoretic limit speed method respectively. In the proposed dynamics simulation method, the vehicle suspension dynamics characteristic, weather and road conditions are considered, and the running state of semi-trailer train can be described accurately.More>
2015, 15(3): 109-117. doi: 10.19818/j.cnki.1671-1637.2015.03.013
Visual simulation model of CVIS
SHANGGUAN Wei, GUO Hong-qian, LIU Peng-hui, CAI Bo-gen, WANG Jian
Abstract: Based on the simulation of cooperative vehicle-infrastructure system(CVIS), the realtime traffic simulation of local region traffic network was taken as an example, the visual simulation model library of CVIS was constructed, and the infrastructure and framework of visual simulation system were established.Visual simulation was integrated as a federate member of whole simulation system, and the typical visual simulation functional models for vehicle-vehicle and vehicle-infrastructure information interactions were built.The visual simulation functional models were divided by using LOD reduction technique, and 5LOD models with different detail degrees were built.By using the functional nodes of DOF, LOD and switch, the related models like intersection signal lamp and vehicles movement in the typical application scenarios were optimized based on node structure, and a similar model geometry node hierarchy structure was constructed.CVIS visual simulation platform including HLA/RTI information interaction andcontrol module, vehicle-infrastructure cooperative data processing module, information interaction module, model guidance and control module, view angle switching module and dynamic display module of model status parameters were constructed.Typical traffic scenario was visually simulated by using modeling optimization technique.Simulation result indicates that by using LOD reduction technique, the model reduction ratio reaches 95.5%, and memory occupancy ratio decreases by 86.3%.By using visual simulation method, rendering efficiency is improved, the efficiency of system simulation is accelerated, and the feasibility of simulation method is verified at typical cooperative vehicle infrastructure scenario.More>
2015, 15(3): 118-126. doi: 10.19818/j.cnki.1671-1637.2015.03.014