3-D DEM Validation using Steel Balls with Regular Packing Arrangements

Abstract

Validation using high-quality physical tests is important to establish the ability of discrete element methods to capture accurately the response of granular materials. A series of triaxial and plane strain compression tests on steel spheres with face centered cubic and rhombic packings was performed. Simulations of these tests were then carried out using the distinct element method (DEM). While the numerical simulations captured the observed laboratory response well, the post-peak response is shown to be sensitive to the coefficient of friction assumed along the boundaries. Simulations of physical tests on hexagonally packed rods have been useful for providing insight into the response of two-dimensional granular materials (O'Sullivan et al., 2002). In this earlier study, biaxial compression tests were performed on uniformly sized rods and on rods with a known size distribution. Recognizing that real granular materials are three-dimensional, this work has been extended to three dimensions. The study considered here examined the response of uniform spheres with both a face-centered-cubic (FCC) packing and with a rhombic packing in compression tests. As with the two-dimensional case, the sensitivity of the response to minor variations in ball size distribution was examined. This paper firstly outlines the physical test procedure, the numerical simulations are then described, and finally some representative results are presented.