A Simple Description of Thick Avalanches at the Surface of a Granular Material

Abstract

Some years ago, Bouchaud et al. introduced a phenomenological model to describe surface flows of granular materials [J. Phys. Fr. I 4, 1383 (1994)]. According to this model, one can distinguish between a static phase and a rolling phase that are able to exchange grains through an erosion/accretion mechanism. Later, Boutreux et al. [Phys. Rev. E 58, 4692 (1998)] proposed a modification of the exchange term in order to describe thicker flows where saturation effects are present. However, these two approaches assumed that the downhill convection velocity of the grains is constant inside the rolling phase, a hypothesis that is not verified experimentally. We have recently modified the above models by introducing a velocity profile in the flow, and analyzed the physical consequences of this modification in the simple situation of an avalanche in an open cell. We here emphasize the physical predictions of our model, and show, in particular, that the thickness of the avalanche depends strongly on the velocity profile.