Stick-slip and force chain buckling

Abstract

Numerous models of stick‐slip have been proposed, yet a key mechanism remains largely unaccounted for in micromechanical formulations. The mechanism in question is that of confined buckling of force chains—a mesoscopic event that involves a collective and coordinated failure at contacts, and is dominated by relative particle rotations. Mounting evidence from both experiments and discrete element simulations suggests that the continual formation and subsequent failure by buckling of force chains is the driving mechanism for stick‐slip. We present herein the first cellular automaton for a granular material under shear that explicitly accounts for force chain buckling. The rule governing the dynamics of the system embodies both a deterministic and a stochastic part. A unique feature of this cellular automaton lies in its micromechanical form, which makes possible an investigation into the effects of particle properties and interactions (i.e. particle size and shape, stiffness properties, interparticle rolling and sliding friction). We use the model to unravel a possible explanation behind the experimentally observed trend of diminishing amplitude of stick‐slip fluctuations with increasing sample size.