Multi-Scale numerical analysis of damage in heterogeneous rocks applied to underground works in an energy transition context. – MSrock

In the actual energy transition context, it is necessary to evaluate the underground potential as a storage and confinement space. Concerning the nuclear electricity production, a sustainable management of the hazardous nuclear wastes is required and is envisaged in deep geological repository. The underground low permeable rock formation has a key safety function by preventing the radionuclide migration. Thus, the stability and sustainability of the underground repository structures have to be assessed throughout a detailed study of the host formation complex behaviour. Geomaterials, such as rocks, are multiphase porous media having a complex heterogeneous structure at different scales. This structure conditions their macroscale behaviour and affects material damage as well as hydraulic properties evolution. Predicting the influence of microstructural characteristics (from mineral scale) on large-scale rupture is a crucial issue in geomechanics. The objective is to develop a multi-scale and multi-physical modelling allowing to predict the rock hydromechanical behaviour around underground excavations from its microstructure. A double-scale approach by finite element method (FEMxFEM) is considered. The microscale material response is used as an implicit macroscale constitutive law, by computational homogenisation. The project focuses on: (i) the relation between microcracking, macro-deformation, and permeability evolution; (ii) the evolution of fluid flow resulting from microcracking; (iii) the reproduction of fractures and drainage within the Excavation Damaged Zones (EDZ) around galleries; and (iv) the global short- and long-term safety of underground repository structures.