Shear lid motion in DEM shear calibration and the effect of particle rearrangement on the internal friction angle

Abstract

Shear cell tests are now commonly applied in particulate calibration procedures for the discrete element method. Usually, only the shear stresses at the shear plane in the particle bed are examined in short-time instances. This work aimed to find the regularities between the internal friction angle, the vertical position of the shear lid, and the rearrangements of particles in the layers during the shear test with the time instance duration of tens to hundreds of seconds. The Schulze RST Ring Shear Tester was used to compare real experiments to numerical DEM models of non-cohesive materials. The shear tests were investigated for different contact models and DEM input parameters. We also simultaneously monitored the overall specimen stiffness, material dilatancy during calibration, and shear stress. Particle bed stiffness increases with increasing shear modulus and coefficient of static friction for two contact models. The internal friction angle, which is a bulk property of the material determined by a set of particle properties, determines the ability (or resistance) to make displacements of rigid non-deformable particles in the shear testing process. The angle of the resultant of the vector of particle motion in space from the horizontal plane correlates with the angle of internal friction (at each location of the shear cell).