EFFECTIVE STRESS IN UNSATURATED GRANULAR MATERIALS: MICRO-MECHANICAL INSIGHTS

Stress transport in an unsaturated granular material is analytically derived. As such, an effective stress tensor related to the mechanical state governed by the interganular forces within the skeleton is identified together with a capillary stress tensor that accounts for the interactions due to the liquid and gaseous phases. Using a Discrete Element Method for modelling an unsaturated granular material, this capillary stress tensor is computed along different loading paths. Knowing the applied total stress, the effective stress tensor is then readily deduced and it is shown that it describes adequately the strength of the unsaturated granular material along various loading paths for any degree of saturation.