热–水–力耦合作用下结晶岩渗透特性演化模型

在热力学框架下，采用细观力学方法，建立热–水–力(THM)耦合条件下低渗饱水结晶岩的各向异性损伤模型，考虑非等温条件下微裂纹水压力作用、法向刚度恢复以及滑动剪胀等细观力学机制对岩石宏观力学性能的影响。在此基础上，采用均匀化方法，建立各向异性损伤诱发的岩石有效渗透特性演化模型，指出损伤岩石有效渗透特性下限估计模型的局限性，进而给出可反映损伤演化过程中微裂纹连通性等细观结构特征的岩石有效渗透特性上限估计模型。采用三轴压缩过程中花岗岩的渗透率变化、高温热处理后花岗岩的单轴压缩性能、TSX巷道开挖产生的围岩损伤与渗透率变化等室内外试验成果对模型进行验证。

A PERMEABILITY EVOLUTION MODEL FOR CRYSTALLINE ROCKS SUBJECTED TO COUPLED THERMO-HYDRO-MECHANICAL LOADING

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.