Avalanches of grains with inhomogeneous distribution of inner mass

Abstract

We study the stability of granular systems constituted by particles with inhomogeneous distribution of inner mass, which is a factor that has not been previously analyzed. In particular, we report experimental results concerning the stability of two-dimensional piles of hollow plexiglass cylinders containing an inserted smaller metal rod. These particles partially fill a rough-edged drum whose rotation produces successive avalanches. The distribution of the maximum angle of stability, the angle of repose, and the avalanche size are analyzed for systems in which the inserts are fixed or free to move. We reveal two interesting effects related to the nonuniform inner mass distribution. On the one hand, the disorder in the array of the center of mass, enhanced in the system of particles with a fixed insert, decreases the stability of the pile. On the other hand, both mobile or fixed inserts lead to larger erosion of the free surface once the avalanche is triggered.