高围压下不同孔隙水压作用时岩石蠕变特性及 改进西原模型

基于高围压下不同孔隙水压作用时细砂岩蠕变试验结果,分析蠕变规律。研究表明：黏弹性模量随孔隙水压增大呈线性递减关系,并根据线性参数随时间变化的数据分布特点,分别用线性函数和幂函数进行拟合,进而得到黏弹性模量随孔隙水压和时间变化的表达式,据此提出一个修正的广义Kelvin模型。根据不同孔隙水压下加速蠕变试验曲线特征,采用指数函数对其拟合,并通过类比的方法引入一个非线性黏性元件,得到一个能反映不同孔隙水压作用下加速蠕变特征的二元件黏塑性蠕变模型,将该模型与修正的广义Kelvin模型串联组成一个新的改进西原模型。基于试验结果,利用优化分析软件1stOpt,对模型参数进行辨识,效果比较理想；对比试验曲线和理论曲线,二者吻合较好,验证了模型的正确性。

Creep properties of rock under high confining pressure and different pore water pressures and a modified Nishihara model

The creep rules of rock are analyzed based on the triaxial creep test results of fine sandstone under high confining pressure and different pore water pressures. With the increase of the pore water pressure, the viscoelastic modulus linearly decreases. The linear function and power function are adopted to fit the linear parameters which change over time. Then an expression for the viscoelastic modulus, which changes with water pressure and time, is derived. Furthermore, a modified Kelvin model is proposed. According to the accelerating creep results under different pore water pressures, a power function is selected for fitting. By introducing a nonlinear element, a two-component visco plastic creep model is obtained for reflecting the accelerated creep characteristics under different pore water pressures. By combining this model with the modified Kelvin model, a modified Nishihara model can be put forward. Using the 1stOpt software to identify the model parameters, the results are satisfactory. A comparison between the test and theoretical curves proves the validity of the proposed model.