高围压高水压条件下岩石非线性蠕变本构模型

Nonlinear creep constitutive model of rock under high confining pressure and high water pressure

基于高围压高水压条件下砂岩三轴压缩蠕变试验结果,分析岩石蠕变规律,选取Burgers模型对低应力水平下的蠕变特性进行描述,效果较为理想。当应力水平高于屈服应力时,岩石在经历一段时间后发生加速蠕变。采用幂函数、对数函数混合方程对加速蠕变段进行拟合,再通过类比的方法提出一个新的非线性黏性元件,并将其与塑性体并联,得到一个可以反映岩石加速蠕变特性的非线性黏塑性模型,将该模型与Burgers模型串联,构建一个新的六元件非线性黏弹塑性蠕变模型,并推导了该模型在常规三轴应力状态下的蠕变本构公式。结合试验结果,运用通用全局优化算法,对提出的非线性黏弹塑性蠕变模型参数进行了辨识,辨识结果验证了新构建模型的正确性与合理性。

According to the triaxial creep curves of sandstone under high confining pressure and high pore water pressure, the creep rule of rock is discussed. The Burgers model is selected to describe the characteristics of creep in the low stress level, which can get nice result. When stress exceeds the yield level, the accelerated creep damage of rock will occur after a period of time. The accelerated creep curves are fitted by the mixed equation of power function and logarithmic function. Then, the method of analogy is used to propose a new nonlinear viscous component, which is in parallel connection with the plastic component to constitute a new nonlinear viscoplastic model. By connecting this model with Burgers model in series, a new six-component nonlinear viscoelastoplastic creep model is acquired. Consequently, the creep constitutive equation in three-dimensional state is deduced. With the test result, the algorithm of Universal Global Optimization is adopted to identify the model parameters, which shows that the proposed six-component nonlinear viscoelastoplastic creep model is available and reasonable.