3D Experimental Characterization of Particle Rotation and Local Dilatancy in Angular Sand

Particle-to-particle interaction plays a major role in characterizing shear strength and deformation characteristics of granular materials. This paper presents an experimental measurement of particle kinematic behavior for very angular sand tested under axisymmetric triaxial loading condition. Synchrotron micro-computed tomography (SMT) technique was used to acquire 3D images of the specimen at 0%, 4%, 8%, and 12% axial strain levels. The results of the analysis showed that some particles rotated more than 20 degrees from the loading direction with a higher rotation about the short diameter of the particle than its long diameter. A definition of local strain and dilatancy based on particle displacement field is adopted from [1] and applied in this paper. There is a high variation in local dilatancy distribution where some particle groups exhibited high dilatancy angles while others showed negligible dilation or contractive behavior.