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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。
Dilatancy is an important deformation behavior of granular materials during loading. The smallest cell of the internal structure of the granular material is described by the porous cell, and the shear force analysis of the single porous cell is used to investigate the dependence of the change of the volume of the granular material on the stress ratio and the shape of the individual cell pores. The micro-mechanism of dilatancy of densely packed particulate materials before compression during shearing is explained. The discrete element numerical simulation was used to obtain the evolution of the cell shape of single pores and the volume deformation of the cell in the biaxial shear process. Discrete elemental numerical results show that the shape of the cellular pores during the loading process increases from the initial isotropic to the direction along the major principal stress and becomes longer and longer. The volumetric deformation first expands after compression and the volume deformation has the localization phenomenon during the loading process. The volume change Large pore cells in the larger deformation, arranged in a narrow strip of inclination. The stress analysis and discrete element numerical results of the composite pore cells show that the dilatancy of the densely arranged particle material is closely related to the geometry of the pore cells and the internal force chain transmission mode at the microscopic scale.