中文摘要：

剪胀性是颗粒材料在加载过程中表现出来的重要变形特性。以孔隙胞元描述颗粒材料内部结构的最小单元,通过对单个孔隙胞元进行剪切受力分析,探讨了剪切过程中颗粒材料体积的改变对应力比和单个孔隙胞元形状的依赖关系,解释了排列密实的颗粒材料在剪切过程中先压缩后剪胀的微观机制。用离散元数值模拟得到了在双轴剪切过程中单个孔隙胞元形状以及孔隙胞元体积变形的演化过程。离散元数值结果表明,加载过程中孔隙胞元形状由初始各向同性到沿大主应力方向变大变长、体积变形先压缩后膨胀,并且体积变形在加载过程中存在局部化现象,体积变化大的孔隙胞元在较大变形时,排列成倾斜的窄带。综合孔隙胞元的受力分析和离散元数值结果表明,致密排列颗粒材料的剪胀性与微观尺度上孔隙胞元的几何结构及其内部的力链传递方式密切相关。

英文摘要：

The shearing induced dilatancy is an important deformation characteristic of granular materials during loading process. As the minimal unit to remain stable under external load, void cell is used to characterize the internal structure of granular materials. Based on the shear process of the individual void cell, it is found that the volume change of void cell is dependent on the stress ratio and the shape of void cell. It is explained the microscopic mechanism of the phenomenon that the dense granular materials compress first and then dilate. The evolutions of the shape of the individual void cell and volume deformation in them during biaxial shear test are simulated by using discrete element method （DEM）. The results show that, the void cell is enlarged along the direction of the maximum principal stress and the volume deformation in the void cell compression first and then dilate as biaxial compression proceeds. Moreover, localization phenomenon is observed in the volume deformation in local void cells from the numerical results, i.e. voids with large dilatancy exhibit in the form of oblique bands at large deformation stage. The mechanical analysis of individual void cells and DEM results of dense granular array show that dilatancy of granular materials is dependent on the microscopic geometry fabric and the transmission of the force in them.