Study on Deformation Mechanism of Saturated Sand Based on Discrete Element Method

Abstract

Based on the discrete element program (particle flow code PFC3D), the effects of the initial void ratio on the macroscopic and microscopic mechanical responses, phase transition state and critical state characteristics of saturated sand are systematically investigated in drained tests. The phenomenon that saturated sand enters the critical state earlier than the laboratory macroscopic results is revealed from the microscopic point of view. The results show that the phase transition state of the saturated sand can be reflected by the extreme values of void ratio, sliding ratio, suspended particle ratio and mechanical coordination number. Compared to the macroscopic parameters stress ratio and volume strain, the microscopic parameters can earlier reveal the critical state of saturated sand. The saturated sands with different initial void ratios have the same anisotropy component at the critical state. At the phase transition state, only the weight of normal contact force anisotropy is in the peak state. During the development of saturated sand from shrinkage to dilatancy, the velocity of particle motion on the diagonal 45° shear surface of the sample is intense and the particle motion is dominated by rotation. The above conclusions expand the current understanding of the deformation mechanism at the phase transition state and critical state of the soil.