岩石非线性黏弹塑性蠕变模型研究

 引进岩石时效强度理论及Kachanov损伤理论，建立以时间变量表示的岩石损伤表达式，并将其与岩石黏塑性流变参数相联系，建立包含加载时间、加载应力等变量在内的岩石黏塑性流变参数非线性表达式，代入西原模型后即建立非线性黏弹塑性蠕变模型。当岩石受到的应力大于岩石长期强度时，岩石即出现损伤，岩石内部的微结构发生变化，岩石的黏塑性流变参数将随时间非线性变化。将建立的模型编入有限元计算程序，并进行数值试验，结果表明所建立的非线性黏弹塑性蠕变模型，可以统一描述软岩和硬岩的蠕变破坏过程，既可以描述软岩在加速蠕变阶段的渐变破坏过程，又可以描述硬岩在加速蠕变阶段的陡然破坏过程，具有广泛的适应能力。将大理岩、盐岩的蠕变破坏试验结果与计算模拟结果进行对比，两者基本吻合，从而验证了模型的正确性。这些成果表明所建模型将具有良好的应用前景。

RESEARCH ON NONLINEAR VISCOELASTO-PLASTIC CREEP MODEL OF ROCK

By using the creep strength theory of rock and the Kachanov damage theory，the relationship of damage with time is firstly proposed. By establishing the relationship of the damage and the viscoplastic rheological parameter，the nonlinear rheological parameter expression is put forward including the factors of time and loaded stress. By incorporating the parameter expression into the Nishihara model，the new nonlinear creep model is established for describing the total three-stage of creep process. When the loaded stress is larger than the long-term strength of rock，the damage occurs，and the rheological parameter begins to present nonlinearity changing with time. By compiling program of the model into finite element method code，the numerical tests are conducted，showing that the proposed creep model can properly describe the creep failure process for soft and hard rocks. It can describe not only the nonlinear failure of the soft rock，but also the abrupt failure of hard rock in the tertiary stage of creep demonstrating the extensive adaptability of the model to different kinds of rocks. The comparison of tests and calculation for marble and rock salt samples respectively further demonstrates the correctness of the model. Obviously，the achieved results show that the proposed nonlinear creep model will find good application to practical engineering.