温度-应力耦合作用下深部盐岩蠕变损伤模型

Creep damage model for deep salt rock under temperature and stress coupling effect

随着我国盐岩储库工程的兴建,浅部适宜矿床逐渐利用殆尽,盐岩储库向深部发展成为必然趋势。为了研究深部盐岩储库实际运营过程中,围岩在三向地应力和温度耦合作用下的蠕变损伤特征,进行了不同温度和应力耦合作用下深部盐岩的三轴蠕变试验。考虑温度和应力对深部盐岩蠕变损伤的影响,认为温度损伤伴随蠕变全过程,所处应力状态达到屈服极限时应力损伤开始发挥作用,且温度和应力与损伤变量之间分别满足Weibull分布和负指数函数的关系。引入分数阶Abel黏壶改进西原正夫模型,建立了一种新的考虑温度-应力耦合效应的黏弹塑性蠕变损伤模型。该模型不仅形式简单,且每个参数都有明确的物理意义,方便模型在数值计算和工程实践中的应用。结果表明:深部盐岩的稳态蠕变率是偏应力和温度的函数,拟合出稳态蠕变应变率本构方程中材料参数A=32.39 MPa-4.83/h、激活自由能Q=7.84×10^(4) kJ/mol、蠕变应力指数n=4.83;不同温度和应力下的黏弹塑性蠕变损伤模型的理论解析解与对应试验数据有良好的吻合度,验证了模型的正确性和精确度。通过蠕变损伤模型各力学元件拟合参数结果验证了温度和应力对岩石蠕变性能的影响规律,证明了所建模型的合理性。所建模型不仅可以精确表征岩石的衰减和稳态蠕变阶段,也能较好地描述加速蠕变阶段的变形特性。

As the demand on the construction salt rock storage increases in China,the shallow suitable deposits have been gradually exhausted,as such,the utilization shift from shallow to deep salt deposits is an inevitable trend.In order to study the creep damage characteristics of surrounding rock under the coupling effect of three-dimensional in-situ stress and temperature during the actual operation of deep salt rock storage,the triaxial creep tests were carried out on deep salt rock specimens under different temperatures and stresses.Considering the influence of temperature and stress on the creep damage characteristic of deep salt rock,it is believed that the temperature damage is accompanied by the whole creep process,and the stress damage starts to play a role when the stress state reaches the yield limit.It is assumed that the damage variables relationship between temperature and stress satisfies Weibull distribution and negative exponential function respectively.A new viscoelastic-plastic creep damage model considering the temperature and stress coupling effect was proposed by in-troducing a fractional Abel dashpot to modify the Nishihara model.The proposed model not only has a simple form and clear physical meaning of parameters,which is convenient for the application of the model in numerical calculation and engineering practice.The results show that the steady-creep rate of deep salt rock is a function of deviatoric stress and temperature.The material parameter A=32.39 MPa−4.83/h,activation free energy Q=7.84×10^(4) kJ/mol and creep stress in-dex n=4.83 in the steady-state creep strain rate constitutive equation are fitted.The theoretical analytical solutions of the viscoelastic-plastic creep damage models under different temperatures and stresses are in good agreement with the corres-ponding experimental data,which verifies the correctness and accuracy of the model.The effects of temperature and stress on rock creep properties were verified by the fitting parameters of each mechanical body of the creep damage model,which proves the rationality of the established model.The theoretical model can not only accurately characterize the atten-uation and steady-state creep stages of rocks,but also well describe the deformation characteristics of accelerated creep stages.