Collapse of Granular Column: Influence of Particle Shape and Polydispersity

In spite of a large effort of the scientific community, a global description of the rheology of granular assembly remains largely elusive. For instance, a systematic study of the influence of particle shape and polydispersity is still lacking while their drastic influence has been demonstrated. To gain a better insight into the mechanical behavior of granular matter, we focus on a canonical set-up: the collapse of columns under gravity. We carried on 3D DEM numerical simulations and experiments of collapses for various granular columns on a frictional plane. Our observations accurately reproduce the previously reported data, the height and run-out distance are determined by the aspect ratio, a=H_i/R_i, of the column. It appears however that the final morphology of the pile is dictated by the existence of a small region of static grains at the bottom of the column. The collapse occurs by a dense flow of falling grains onto the cone of static grains. In this presentation, we will discuss the origin of this static zone and how it influences all the properties of the granular pile during the collapse. A peculiar attention will be drawn to the particle shape.