Guizhou Expressway Development Corporation

Guiyang, China

Guizhou Expressway Development Corporation

Guiyang, China
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Bai L.-D.,Wuhan University | Bai L.-D.,Guizhou Expressway Development Corporation | Bai L.-D.,TU Berlin | Xiang W.,Wuhan University | And 2 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2012

The problems and solutions of applying the bender element method to determine the maximum shear modulus (G max) of sand are investigated by conducting resonant column (RC) and bender element (BE) tests on four dry sands obtained from Germany. The study indicates that the start-to-start method is more reliable to identify the time of shear wave propagation in specimens compared to other methods. In BE tests, the excitation frequency of input waves has influence on the tested Gmax, and this influence is dependent on soil types and reduced by increasing confining pressure. A comparison between RC and BE tests shows that G max by both methods may be well expressed as a linear equation; for the Berlin sand and Braunschweig coarse sand, there exists a threshold G max below which G max by BE tests (G max (BE)) is greater than that by RC tests (G max (RC)), however beyond which the G max (BE) is smaller than G max (RC) and the distance between both increases with increasing stiffness soil. In practice, it is suggested that the input voltage with proper high frequency is preferred for BE tests, as compared with RC tests.


Bai L.-D.,Wuhan University | Bai L.-D.,Guizhou Expressway Development Corporation | Bai L.-D.,TU Berlin | Xiang W.,Wuhan University | And 2 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2012

The effects of vibration history on nonlinear dynamic properties of dry sand are studied by applying torsional previbration using the non-resonant vibration mode by means of the Stokoe resonant column apparatus. The study shows that, for a given sand sample, there is a threshold number, below which G max decreases and beyond which it increases with the number of cycles. Normalized shear modulus is not affected by preloading frequency but damping ratio increases with preloading frequency under the confining pressure under which previbration is applied. The normalized shear modulus decreases and the damping ratio increases with the number of cycles. Reloading confining pressure may decrease and unloading confining pressure may further magnify the effects of the vibration history on the normalized shear modulus and the damping ratio. The effects of vibration history on the normalized shear modulus and the damping properties result from for the jointed effects of wear process and reorientation of interparticles in vertical direction.


Zhong J.,Wuhan Bridge Science Research Institute Ltd | Zhong J.,Important Laboratory for Bridge Safe and Health | Huang K.,Guizhou Expressway Development Corporation | Li X.,Wuhan Bridge Science Research Institute Ltd | Li X.,Important Laboratory for Bridge Safe and Health
Applied Mechanics and Materials | Year: 2011

The fatigue truck model is an important parameter in a fatigue evaluation, a 3-axle fatigue truck model was developed based on the weigh-in-motion traffic data and an analytical bridge model in the montane highway of Southwest China. The truck traffic data shows that the fatigue damage was dominated by the 6-axles trucks,a 3-axle fatigue truck model was developed based on the 6-axle truck statistic data,the damage accumulations caused by the Proposed fatigue truck righty meet the actual damage accumulations. Based on the cumulative probabilitie of the moment ranges, the peak stress range is suggested to be a stress level at 3 times of the effective stress range because of overload,however,the ratio of the effective stress in AASHTO was 2 times.The damage accumulations obtained from the simulation of the truck database were compared with BS5400,AASHTO and Proposed fatigue truck, Proposed fatigue truck and AASHTO fatigue truck with the actural daily flow of trucks are suggested in the montane speedway of Southwest China ,BS5400 is impropriety which relatively overestimate the damage. © (2011) Trans Tech Publications.


Bai L.,Hubei Engineering University | Bai L.,Guizhou Expressway Development Corporation
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2011

Effects of number of cycles, preloading frequency, dynamic prestress ratio, density, sampling technique, preshearing mode and duration of confinement on the maximum shear modulus (Gmax) of sand were systematically investigated by applying the preloading to the tested dry sand samples using the non-resonant vibration supplied by resonant column apparatus. Testing results indicated that: (1) The Gmax of dry sand decreased with increase of number of cycles when it was lower than a threshold number. At this threshold number, the maximum reduction of Gmax might be over 20% for some cases. (2) However, beyond this threshold number, Gmax started to recover with increasing number of cycles. The reduction of Gmax with number of cycles decreased with the increases of preloading frequency, dynamic prestress ratio and sample density; but their qualitative relationship was not affected by the sampling method and preshearing mode. The increase of Gmax with confinement duration was minor and the increase rate was slightly greater for the sample with preloading than that without preloading. The variation of Gmax with number of cycles may be accounted for the jointed effects of sample densification, interparticles wear process and particles reorientation or coordination number reorientation.


Bai L.,Hubei Engineering University | Bai L.,Guizhou Expressway Development Corporation | Xiang W.,Guizhou Expressway Development Corporation
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2012

Effects of torsional shear frequency, input voltage and specimen torsional stiffness on the torque factor are systematically investigated on the basis of a number of torsional shear tests on six aluminum calibration bars using the combined torsional shear resonant column apparatus. Results indicate that the torque factor of this type of device slightly decreases with increasing torsional shear frequency and input voltage, but significantly increases with increasing torsional stiffness of specimen, due to the inherent design limitation of the electromagnetic drive system. When the constant torque factor obtained from the traditional calibration method, which is suggested by the manufacturer, is employed to analyze the shear modulus of calibration bar, testing result is significantly underestimated with the error of 14% for the greatest stiffness calibration bar (Bar #6), and overestimated with the error of 25% for the smallest stiffness bar (Bar #1). Therefore, a new calibration procedure is proposed to overcome the error induced by the inherent design weakness of the drive system. It can minimize the testing error within 3% for torsional shear tests conducted by this type of resonant column device.

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