Friction-induced breakdown of avalanches scaling in granular flow

Alberto Petri (CNR-ISC Rome)

At a low shear rate, a granular bed flows intermittently in the form of distinct avalanches. Simple stochastic models predict that these avalanches will be random in nature, yet self-similar on average. However, experiments have shown that scale invariance holds for small avalanches, but not for large ones. Through long-lasting experiments, we have demonstrated that the breakdown of scaling invariance is associated with a change in friction behaviour when transitioning from small to large events. Additionally, results based on a more elaborate model than those commonly adopted show that this change can be explained within the framework of rate-and-state friction laws, which include ageing and weakening effects. The model also reproduces the asymmetry displayed by larger avalanches, clarifying the different effects of inertia and friction.