Excavation damaged zone modelling including hydraulic permeability evolution in unsaturated argilaceous rock

The drilling of galleries induces damage propagation in the surrounding medium and creates the Excavation Damaged Zone (EDZ) in which the material properties are modified. The prediction of the fracture structure and flow properties evolution within this zone are major issues especially in the context of underground nuclear waste storage. Since experimental results indicate that shear strain localisation appears prior to fractures, we model the EDZ with strain localisation in shear band mode using the coupled local second gradient model. The evolution of the intrinsic hydraulic permeability inside the fractures is taken into consideration as well as the influence of gallery ventilation on the rock desaturation. The numerical results provide information about the damaged zone extension, structure and behaviour with good correspondence to in situ measurements and observations.