一种新的岩石非线性流变损伤模型研究

传统岩石流变模型由线性元件组合而成,不能很好地描述流变过程中的加速流变阶段,通过分析岩石流变过程中微裂纹的压闭和扩展过程,将损伤力学引入岩石流变模型中,采用Kachanov提出的损伤律,将岩石流变过程分为阶段一（衰减、稳态蠕变阶段）和阶段二（加速蠕变阶段）两个部分,推导了岩石在两阶段中损伤演化方程,通过参数敏感性分析发现应力水平的大小对损伤演化过程有较大影响。结合有效应力观点建立了岩石非线性损伤流变模型,该模型能较好的描述岩石的衰减、稳态和加速流变阶段,同时简要分析了模型的松弛特性。采用该岩石非线性损伤流变模型对泥岩在围压为5 MPa与轴向偏应力水平为43 MPa的蠕变试验结果进行了模拟,验证了损伤流变模型的合理性,保持其他参数不变,更改应力水平的大小,得到不同应力水平下的非线性损伤蠕变模型曲线,与试验结果较为相符,

A new nonlinear rheological damage model for rock

The traditional rheological models for rock consisting of linear components can not describe very well the accelerating creep stage. The closure and expansion of microcracks in the process of rock rheology are analyzed, and the damage mechanics is introduced to construct a new rheological model. The damage law put forward by Kachanov is adopted and the rheological process of rock is divided into the first phase (the initial attenuation creep stage and the steady-state creep stage) and the second phase (the accelerating creep stage), and the corresponding damage evolution equations are deduced. By analyzing the sensitivity of creep parameters, the stress level has a great influence on the damage evolution characteristics. The nonlinear rheological damage model for rock is established based on the effective stress law, and the stress relaxation property is also analyzed. This nonlinear rheological model can describe the complete creep curve very well. Using this model to simulate the whole creep process of mudstone under the confining pressure of 5 MPa and axial deviatoric stress of 43 MPa, it shows, that the nonlinear rheological damage model is right and reasonable. Several calculated damage model curves under different stress levels are shown, which are coincident with practical curves. By comparing the creep test curves with those of Nishihara visco-elastioplastic rheological model, the difference is great between the model curves and the practical ones especially at the accelerating creep stage.