Diffuse failure in geomaterials: Experiments and modelling

While localized failure has been extensively studied, diffuse failure modes are still not characterized from an experimental point of view and not described by proper criteria from a theoretical point of view. The purpose of this paper is to tackle both these questions by considering, in a first part, undrained triaxial loading on very loose sands and the failure mode occurring at q-peak, and, in a second part, the bifurcation domain of sands in plane strain conditions through strain proportional paths and incrementally piece-wise linear and non-linear constitutive relations.