A model of capillary cohesion for numerical simulations of 3D polydisperse granular media

We present a 3D discrete-element approach for numerical investigation of wet granular media. This approach relies oil the basic laws of contact and Coulomb friction enriched by a capillary force law between particles. We show that the latter can be expressed as a simple explicit function of the gap and volume of the liquid bridge connecting a pair of spherical particles. The length scales involved in this expression are analyzed by comparing with direct integration of the Laplace-Young equation. We illustrate and validate this approach by application to direct shear and simple compression loadings. The shear and compression strengths obtained from simulations reproduce well the experimental measurements under similar material and boundary conditions. Out findings clearly show that the number density of liquid bonds in the bulk is a decisive parameter for the overall cohesion of wet granular matetials. A homogeneous distribution of the liquid within the bridge debonding distance, even at low volume contents, leads to the highest cohesion. The latter is independent of the liquid content as far as the liquid remains in the pendular state and the number density of liquid bonds remains constant. Copyright (c) 2007 John Wiley & Soils, Ltd.