Angle of repose and stress distribution of sandpiles formed with ellipsoidal particles

The properties of a sandpile such as angle of repose and stress distribution are affected by many variables, among which particle shape is one of the most important. In this work, ellipsoids which can represent a large range of shapes varying from disk- to cylinder-type are used. The discrete element method is employed in order to conduct controlled numerical experiments. The results confirm the general findings reported in the literature. It also shows that with aspect ratios deviating from 1.0, the angle of repose increases significantly, but disk-type shape and cylinder-type shape follow different variation trends. Empirical correlations between the angle of repose and aspect ratio or sphericity are proposed. The analysis on the stress distribution shows that particle shape affects the magnitude of the normal contact force between particles significantly, with spheres being the smallest. The pressure distribution underneath sandpiles is featured with a relatively constant normal pressure in the central region rather than a dip. It is confirmed that non-spherical particles have more pronounced stress dip than spherical particles.