Deformation characterizations of granular material in 2D dense assembly subjected to shearing

Abstract

This experimental study explores the deformation characterizations of granular material in dense assembly subjected to shearing. The 3D printed elliptical particles with eccentricity of 0.2 were used to simulate the real granular material (sand). A biaxial system modified from the CKC triaxial system, including a loading frame, a tailor-made 3D printed biaxial cell, the volume-measuring device and a control unit, was utilized for the experimental test. The dense assembly was randomly packed with elliptical particle. General dilatancy behaviour was observed for this assembly during shearing. The inherent fabric evolutions based on contact normal and particle orientation were explored. The fabric anisotropy of the assembly was intensified by shearing. In the examinations, the motion of a particle pair is divided into three types, i.e., the contact deformation, the Type 4 rolling, and the rigid motion. Each part of the motion has different contributions to the sample deformation at different strain levels. The normal component of contact deformation dominates volumetric contraction at small strains and dilation at larger strains. The rigid body rotation even leads to contraction in sample. For the sample distortion, it is mainly due to the rigid body rotation and the normal component of contact deformation makes the second contribution. The tangential component of contact deformation and the Type 4 rolling relatively have small contributions to both volumetric strain and sample distortion.