Abstract
The dynamics of a two dimensional pile constituted by spherical grains organized in parallel layers is investigated theoretically. Only three effects are taken into account in the model: driving by gravity, non-local dissipation due to shocks and trapping of grains by the bumps of the underneath layer. This is sufficient to recover the basic properties of granular avalanches: the transition between static and flowing state is hysteretic ; the pile does not flow on the whole height but only in a layer at the surface ; the velocity profile inside the flowing layer is approximately linear and is followed by a creep motion in the (quasi) static part. The flowing height increases as a function of the pile angle and tends to infinity for a critical angle. The dependence of this critical angle with the static angle, the restitution coefficient and the moment of inertia is investigated.