A Multi-Scale Homogenized Hydro-Mechanical Coupled Model for Fractured Rocks

Abstract Based on the multi-scale structural characteristics of fractured rocks, a hydro-mechanical coupled model was formulated by a multi-scale homogenization method under the framework of thermodynamics. The proposed model simultaneously accounts for the deformation and permeability variation in fractured rocks induced by the structural alterations of both arbitrarily-distributed microcracks of smaller scales and group-orientated fractures of much larger scales under coupled hydro-mechanical loadings. The impacts of many important mechanisms are considered, such as the interstitial water pressure, microcrack initiation and propagation, normal stiffness recovery caused by microcrack compression closure, frictional sliding of closed microcracks, shear sliding and dilatancy of fractures, fracture surface asperities degradation. Numerical simulations of Stripa tunnel excavation performed with the proposed model, show that it’s important to account for the variations of both small-scale microcracks and large-scale fractures for better characterizing the excavation-induced permeability change in the area adjacent to the excavation face.