For saturated quasi-brittle rocks containing randomly distributed microcracks, the interstitial water pressure has an important impact on the internal deformation and strength. Fully considering the microscopic characteristics and evolution of material, a multiscale damage constitutive model with the hydro-mechanical coupling under undrained condition was established to study the damage behaviors of quasi-brittle rocks. This model is based on the linear homogenization method of Mori-Tanaka and the irreversible thermodynamics theory. For the small perturbation, an analytical expression of the strength, suitable for the conventional triaxial test under undrained condition, was derived through the remarkable hydro-mechanical coupling analysis. The proposed multiscale model was finally applied to simulate a series of undrained triaxial compression tests of sandstone,where the laws of stress-strain curves and interstitial water pressure in the mechanical loading process were reasonably demonstrated.%以水-力耦合条件下准脆性岩石的损伤行为为研究对象,充分考虑材料的细观特征及其演化规律,结合Mori-Tanaka线性均匀化方法和不可逆热动力学理论建立了在不排水条件下水-力耦合损伤多尺度本构模型.基于小扰动假定,通过水-力耦合分析,推导了不排水常规三轴试验条件下多尺度模型的强度的解析表达式.通过模拟不同围压下砂岩的三轴压缩不排水试验,验证了模型的有效性,并分析了岩石在损伤演化过程中应力应变曲线和孔隙水压力的演化规律.
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