中文摘要：

基于PFC2D非圆颗粒单元的二次开发,对砂土直剪力学过程进行了非圆颗粒仿真模拟,分析了数值试样的应力–剪胀关系并与实际砂土进行对比,探讨了颗粒位移与颗粒旋转特征及其与剪切带演化的内在关联,研究了主应力与主应变增量的非共轴效应,揭示了细观组构各向异性的演化规律及其与宏观剪切强度之间的宏细观关联。研究结果表明,数值试验能够较好的模拟实际砂土的应力–剪胀关系和剪切过程主应力与主应变增量的非共轴效应;剪切带的演化与颗粒位移和颗粒旋转密切相关,颗粒形状影响剪切带的厚度;试样宏观的剪切强度主要受控于粒间法向接触力的分布及其各向异性演化;整个加荷过程中,剪切带内大主应力的偏转方向与法向接触力各向异性的主方向保持了良好的一致性。

英文摘要：

The main objective of this study is to explore the macro-and micro-scale responses of sand in the direct shear tests by discrete element simulation.Non-circular particle element is self-developed in particle flow code in 2-dimension（PFC2D）.The stress-dilatancy relationship of numerical samples is compared with that of real sand.The evolution of shear band is studied in relation with the variation of particle displacement and rotation.The effect of non-coaxiality between the directions of principal stress and principal strain increment is examined.Special attention is focused on the evolution of stress-induced fabric anisotropy during the shear loading.It is found that the discrete element simulation has a good ability to reproduce the stress-dilatancy relationship and non-coaxiality effect of real sand.The formation of shear band is strongly dependent on the distributions of particle displacement and rotation.A strong correlation between the shear strength and the evolution of normal contact force is evident in the simulation results.Coincidence between the orientation of normal contact force anisotropy and the direction of the major principal stress has been observed during all stages of shear loading.