SIMULATION AND MICRO-MECHANICS ANALYSIS OF INHERENT ANISOTROPY OF GRANULAR BY DISTINCT ELEMENT METHOD

The particles tend to be spatially arranged in directional orientation after the paving of granular materials, and thus leading to the inherent anisotropy of mechanical property. Based on the actual irregular shape of granular materials, three-dimensional complex shape particles were modelled utilizing distinct element method to simulate the interlocking between particles. Five numerical test specimens with different bedding angles and an isotropic specimen were established respectively, and the mechanical properties of various specimens were compared during the triaxial compression simulations. Besides, the fabric tensor was introduced to quantify the anisotropy, the rose diagram was drawn to exhibit the distribution characteristics of contact normal and contact force, and then the development of anisotropy was investigated. It is shown that, as the long axis of particles change toward the horizontal direction, the stress ratio and the shear dilatancy of specimen increase continuously. Compared with isotropic structure, the peak stress ratio and the maximal volume compression strain of anisotropic structure when the bedding angle \theta=0^\circ is 12.6% and 18.8% larger respectively. This is because the rotation and contact sliding ratio of particles is smaller, the internal adjustment time is shorter, and specimen can be sheared more densely. The inherent anisotropy has little effect on the distribution characteristics of contact force, but significantly affects the distribution characteristics of contact normal. When \theta is 90^\circ, the contact normal anisotropy coefficient drops quickly and then gradually increases during the shear process. Otherwise, the coefficient shows a steady or slight drop trend after an increase, and the coefficient grows faster as the \theta decreases.