ABSTRACT
The stability of granular slopes is related to the existence of two angles. The static angle of avalanche θc characterizes the maximum slope angle compatible with static equilibrium. Equivalently, θc is the slope angle for which slope failure and surface avalanche are incipient. The dynamical angle of repose θd is the angle at which the surface of the flow is stabilized after a surface avalanche was triggered, with θd <θc. The angle of hysteresis, defined as the slope interval [θd , θc] is typically of few degrees.
