Behavior of model cohesive granular materials in the dense flow regime

Abstract

Molecular dynamics simulations are applied to the study of the constitutive law for dense flows of cohesive grains. We focus on a simple cohesive model in which the important parameters are the tensile strength and the friction coefficient in contacts. The study of plane shear flows highlights a simple dependence of the macroscopic internal friction law on both the shear state and the cohesion intensity. Such state variables boil down to two dimensionless parameters, the inertial number and the cohesion number, which respectively compare the inertia of grains and the attractive forces with the applied confining forces. In the case of a gravity-driven flow down a slope, the cohesion number increases near the free surface, where cohesion-enhanced friction leads to plug flow.