Force Chains and Resonant Behavior in Bending of a Granular Layer on an Elastic Support

In this paper we investigate the interaction between a granular layer and an elastic foundation using a coupled Discrete Element Method-Finite Element Method (DEM–FEM) computational model. We use this dynamics code to simulate quasi-static bending of the granular layer and we observe the changes taking place in the structure of the force chains for two cases: with and without rolling resistance. A reversal of the arches formed in the force chains leads to a bending resistance similar to that observed in dynamic experiments on resonant behavior under bending of a layer of sand in a container with an elastic bottom. The behavior of the force chains generated during bending may lead to enhanced mixing in vibrated granular media. In free vibration, the granular-layer/elastic-beam system behaves like a mass-loaded beam with no contribution to the stiffness from the granular layer, independent from the layer thickness and rolling resistance. This is observed to be due to the absence of the reversal of the force chain structures noticed in the quasi-static case when a push-up force bends the system upwards and the force chains rest against the middle of the beam and the side walls. Future studies are required for explaining the experimental observations related to the particle-size dependence of the bending stiffness in a granular layer as well as the resonant behavior of the system under forced bending vibrations.