Modelling the fracture generation in EDZ

Tunnelling in clay formations may induce strain localisation and fracture, as recently observed in Mol underground laboratory. A hydro mechanical modelling with a strain softening constitutive model allows to reproduce such phenomena. The results are strongly dependent on the hydraulic boundary condition at the tunnel face, which has to be better analysed. Deep underground storage of nuclear waste induces severe conditions on the host rock (especially of clay/clay stone) and on the engineered barrier, which is generally made of swelling clay. The Iong-term integrity of the permeability barriers has to be proved. The good understanding of such disposal needs high-Ievel numerical models, including different aspects: thermal and partial saturation hydraulics effects, suction-mechanics interaction, strain localisation and fracture prediction. Highly coupled non-linear finite element codes are today necessary to tackle such challenge. (author)