一种新的岩石非线性黏弹塑性蠕变模型研究

为了克服传统元件组合模型不能描述岩石蠕变过程中非线性特征的缺陷,首先根据加速蠕变阶段的应变和应变率随蠕变时间急剧增大的特点,建立黏塑性应变与蠕变时间的指数函数关系并提出非线性黏塑性体.将该非线性黏塑性体与广义Burgers蠕变模型串联,建立可以描述岩石全蠕变过程的非线性黏弹塑性蠕变模型,根据叠加原理得到一维应力状态下的轴向蠕变方程.然后基于塑性力学理论指出岩石三维蠕变本构方程建立过程中的不足之处,并给出非线性黏弹塑性蠕变模型合理的三维蠕变方程.最后采用不同应力水平下砂岩轴向蠕变试验对模型合理性进行验证,结果表明:拟合曲线与试验曲线吻合度较高,所建蠕变模型能够很好地描述砂岩在不同应力水平下的蠕变变形规律,尤其对加速蠕变阶段的非线性特征描述效果很好,验证了模型的合理性.

A New Nonlinear Viscoelastic-Plastic Creep Model for Rocks

 In order to overcome the disadvantage that the traditional component combination model cannot describe the non-linear characteristics of rock creep process, firstly, the exponential function relationship between the viscoplastic strain and creep time is established according to the characteristics that the strain and strain rate increase sharply with creep time in the accelerated creep stage. A non-linear viscoplastic body is also proposed. The non-linear viscoplastic body is connected in series with the generalized Burgers creep model to establish a non-linear viscoelastic-plastic creep model that can describe the whole creep process of rock. According to the superposition principle, the axial creep equation under one-dimensional stress state is obtained. Then, based on the theory of plastic mechanics, the shortcomings of the three-dimensional creep constitutive equation of rock are pointed out, and the reasonable three-dimensional creep equation of the non-linear viscoelastic-plastic creep model is given. Finally, the rationality of the model is verified by the axial creep test of sandstone under different stress levels. The results show that the fitting curve is in good agreement with the experimental curve. The creep model can well describe the creep deformation of the sandstone under different stress levels, especially for the non-linear characteristics in the accelerated creep stage, which verifies the appropriateness of the proposed model.