Some experiments on granular surface flows

We report here an experimental study on surface granular flows. The granular packing is made of monosize glass beads initially poured in a box with controlled humidity. We have first studied the angles before and after the avalanche, and the mass displaced out of the box during the avalanche as a function of the number of layers of the packing. For small packings, up to approximately 10 layers, the stability of the system is significantly affected by the bottom rough surface. On the contrary, for thicker systems, the critical angles are unchanged with variations of the number of layers. In a second experiment, in the same apparatus in 3d and also in 2d, we have studied flow of a mass of grain on a surface near the situation where no accretion nor erosion exist (at the neutral angle). The influence of the geometry of the system is investigated.