Micro-statics and micro-kinematics of capillary phenomena in dense granular materials

Abstract

A capillary stress tensor and an effective stress tensor are defined in DEM simulations of spheres packings with capillary effect. It is shown that induced fabric anisotropy results in an anisotropy of the capillary stress, so that any stress‐like variable used to represent the effect of capillarity in granular materials should be represented by a non‐spherical tensor. The response of a sample to small isotropic stress increments is also presented, the loading being imposed either by a small variation of the stress imposed at boundaries (method A) or by a variation of matric suction (method B). The comparison of the results, with emphasis on micromechanical aspects, shows some differences between the results obtained with methods A and B, even though the increment of effective stress is the same in both cases. The effective stress concept in unsaturated granular materials is questionned on the basis of these results.