基于离散元法的静止土压力系数分析

Analysis of coefficient of earth pressure at rest based on discrete element method

采用三维离散元法(DEM)对不同初始孔隙比的粒状土进行一维压缩0K试验模拟。对比了传统定义静止土压力系数0K以及增量型定义静止土压力系数0K?,分析了静止土压力系数的影响因素(初始应力状态、初始孔隙比和应力历史),检验了Jaky公式及Mayne和Kulhawy公式的适用性。结果表明,对于初始等向围压试样,随着竖向压力的增大,0K减小,则0K?先增大到峰值后再减小;对于初始0K状态试样,0K、0K?随着竖向压力的增大均减小。0K、0K?分别在竖向压力达到初始等向围压6~10倍及4倍左右达到稳定值,即真实的0K值;0K、0K?随孔隙比减小而明显减小。应力历史对0K有显著影响,对于相同应力状态的加载和卸载阶段0K差别很大。Jaky公式及Mayne和Kulhawy公式计算结果与数值模拟结果有一定差异,采用峰值摩擦角比采用残余摩擦角的公式计算结果更接近数值模拟结果。

The coefficient of earth pressure at rest0 K of granular soils is revisited by discrete element method(DEM) simulation. The effects of confining pressure, soil density and over-consolidation ratio(OCR) on the 0K are systematically investigated. The coefficient of earth pressure at rest defined in the conventional form0 K and in the incremental form0 K ? are compared; and the effectiveness of Jaky's equation and Mayne and Kulhawy's equation in predicting0 K is examined. The results show that the K0and0 K ? generally approach their 'true'(or constant) values when the applied vertical stress is 6-10 times and 4 times of the initial isotropic stress. Meanwhile, the0 K value remarkably decreases as void ratio decreases. The OCR has a significant effect on the K0 value and the K0 value is quite different in loading and unloading stages for the same OCR value. Better prediction is obtained by Jaky's equation and Mayne and Kulhway's equation if peak friction angle is used, although the prediction may be quite different from the measurement.