(1. State Key Laboratory of Water Resources and Hydropower Engineering Science，Wuhan University，Wuhan，Hubei 430072，
China；2. Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering，Ministry of Education，Wuhan University，
Wuhan，Hubei 430072，China；3. Royal Institute of Technology，Stockholm 10044，Sweden)
Abstract：An anisotropic damage model was established for fluid-saturated crystalline rocks of low permeability in coupled thermo-hydro-mechanical(THM) loading conditions by using the micromechanical approach in the framework of thermodynamics. The proposed damage model accounts for the impacts of some important micromechanisms，such as the interstitial water pressure，normal stiffness recovery induced by compressed microcracks and sliding and shear dilatancy of closed microcracks，on the macromechanical properties of rocks under non-isothermal condition. On this basis，using various homogenization approaches，estimates were presented for the variations in effective permeability of cracked rocks induced by anisotropic damage propagation. The predictive limitations associated with the lower bound estimates for the effective permeability of damaged rocks were discussed；and a rigorous upper bound estimate was then presented to account for the influence of some important microstructural features，such as the connectivity and persistence of microcrack system，on the permeability variation. Existing laboratory tests on granite samples for damage-induced variation in permeability in triaxial condition and for uniaxial mechanical response after high-temperature thermal treatment，together with the in-situ measurements of excavation-induced damage zone and permeability variation in the surrounding rock of the TSX tunnel，were used to validate the proposed models.
2013, Vol. 32 
