Instabilities in slowly driven granular packing.

In this work, a digital imaging technique is used to study the superficial fluctuations observed when a granular packing is slowly driven to the threshold of instability. The experimental results show the presence of three types of events. Small superficial rearrangements of grains are observed during all the experiments.

Influence of the number of layers on the equilibrium of a granular packing.

This paper reports an experimental study on avalanches in a granular material contained in a confined geometry. The granular packing is made of monosize glass beads initially poured into a box that is slowly inclined until an avalanche takes place at a critical angle straight theta(M) (maximum angle of stability). The avalanche involves a decrease of the surface slope until a second critical angle straight theta(r) (angle of repose) is reached.