Shockwaves in Jammed Ductile Granular Media

We investigate shock propagation in confined, frictionless granular media using discrete element simulations with an elastoplastic contact law. Depending on the level of confinement and loading, elastoplastic systems exhibit a weak or strong shock propagation response similar to an elastic Hertzian system although the details of the shock development differ markedly from the elastic case. Two modes of dynamic stress propagation are observed based on the shock intensity regime: Weak shocks carry the stresses via the initial contact path while strong shocks form new contact networks behind the front. However, unlike for elastic shock propagation, there is an upper bound to the front velocity of strong shocks that depends on the maximum intergranular contact stiffness. Since elastoplastic contact is a dissipative process, results show that dissipation is enhanced with confining pressure in the weak shock regime.