Numerical modelling of biaxial compression tests for granular materials with inherent anisotropy using DEM

The deformation of granular materials with inherent anisotropy is dependent on the principal stress direction relative to the bedding plane. In order to investigate the micro deformation process of anisotropic granular materials with discrete element method(DEM), a numerical model was verified by two series of biaxial compression tests firstly. The experiments were conducted on the ideal 2D ellipse-shaped iron rods under three cell pressures and four different major principal stress directions. On this basis, the development of shear band under four different major principal stress direction loadings was studied by analyzing the particle displacement and rotation at different deformation stages. Further, the long axis orientation of particles and void ratio inside and outside shear band were investigated. It was found that, under the loading with different major principal stress directions, the long axis orientation of particles inside the shear band tends to approach the same direction, and the same tendency was also found for the void ratio inside the shear band.