Constitutive model for unsaturated granular media

A simple microstructural constitutive model for unsaturated granular media has been developped, based on the calculation of (mechanical and capillary) intergranular forces in regular packings of isodiametral balls, deformable and elastic. To take into account the influence of density, several types of packings were considered. The predictions of the model were compared to experimental data on various paths. A general agreement was observed, both in the case of paths involving elastic deformations or no deformations (drying-wetting paths, small strains isotropic paths..), and for the determination of failure criteria (shear and unconfined compression paths). On these paths, it was shown that the behavior of the material could be described by using a generalised effective stress concept, whose expression is given in the paper.