Quantitative Comparison of Two-Dimensional and Three-Dimensional Discrete-Element Simulations of Nominally Two-Dimensional Shear Flow

Abstract

Results obtained from numerical simulations of direct (or ring) shear tests on ASTM standard graded (Ottawa) sand using the discrete-element method with periodic boundary conditions in both two and three dimensions are reported. The data obtained from these simulations are quantitatively compared to experimental data for ASTM standard graded sand. The results show that the three-dimensional (3D) effects of nonplanar interparticle contact forces and particle motion are significant in the 3D discrete-element method simulations, even during nominally two-dimensional (2D) shear flow. Moreover, the 3D discrete-element method simulations accurately predict the peak and residual friction angles of ASTM standard graded sand. On the other hand, the 2D discrete-element method simulations fail to accurately predict the peak and residual friction angles. It is argued that the failure of the 2D discrete-element method simulations and the success of the 3D discrete-element method simulations in providing quantitatively accurate predictions of peak and residual friction angles are attributable largely to the respective absence or presence of 3D effects, including nonplanar interparticle contact forces and nonplanar particle motion, in these discrete-element method simulations.