制样方法对砂土液化力学性质影响的离散元模拟

Effects of Sample Preparation Method on Sand Liquefaction Mechanical Properties with Discrete Element Simulation

摘要:

基于PFC2D软件对湿捣法和落砂法制备的砂土试样进行不排水循环剪切试验模拟，分析了砂土颗粒在动力加载过程中细观结构的变化规律。结果表明，施加荷载后，试样颗粒长轴方向在压缩侧偏向水平，拉伸侧趋向竖直，而接触法向的趋势则与之相反，二者的各向异性系数均逐渐上升。试样整体配位数随荷载的作用逐渐下降，液化后于0~3范围内波动。湿捣法试样比落砂法试样的各向异性程度更小，液化所需的加载循环数更多，即具有更高的抗液化强度。密实度越高，两种试样的液化强度差别越大。

Abstract:

PFC2D software was used to simulate sand samples prepared by moist tamping method and deposition method. Undrained cyclic loading tests were performed on samples to analyze the microstructure changes during the dynamic loading process. The test results indicated that the long axis direction of sand particles tended to distribute horizontally on the compression side but vertically on the extension side when cyclic loading was applied. Although the distribution of the normal directions of particle contacts was contrary to the long axis direction， both anisotropy coefficients were increased gradually with the increasing of cyclic number. Besides， the coordination number of the samples decreased and finally fluctuated within the range of 0-3 after liquefaction. The samples obtained from moist tamping method exhibited less anisotropy than the deposition samples. Thus， the former one required more loading cycles to reach liquefaction， which implies the layered samples owned higher resistance to liquefaction. The differences in liquefaction resistance between two samples were more obvious for dense sand than medium-dense sand.