横观各向同性岩石蠕变性质与本构模型研究

Creep behaviors and constitutive model of transversely isotropic rocks

层理的存在使得炭质板岩呈现出横观各向同性性质。开展了水平层理试样和竖直层理试样的三轴压缩蠕变试验,研究了不同层理的炭质板岩在不同加载路径下的蠕变特性,分析了蠕变流动方向特征,发现水平层理试样和竖直层理试样蠕变流动方向差异明显;根据蠕变试验结果,提出了横观各向同性岩石蠕变本构模型,该本构模型由基于广义八面体剪应力的蠕变势函数和非关联流动法则构成,蠕变方程采用基于不可恢复应变的内变量蠕变方程;采用不可恢复应变为内变量来描述炭质板岩的蠕变特性,考虑了初始加速蠕变对初始蠕变的影响;提出了模型参数确定方法,并采用试验数据和文献数据对所提模型与参数求解方法进行了验证。研究结果为了解岩石横观各向同性蠕变特性和丰富岩石力学基本理论提供了基础。

The bedded carbonaceous slate exhibits transversely isotropic creep properties. The creep behaviors of carbonaceous slate are studied using the triaxial compressive creep tests on horizontal bedding specimens and vertical bedding specimens. The creep flow direction is analyzed with the experimental data. It is found that the creep flow directions of the horizontal and vertical bedding specimens are different. A creep constitutive model for transversely isotropic rocks is proposed. The constitutive model is composed of creep potential function based on the generalized octahedral shear stress and creep non-associated flow law. The creep equation is formulated as a function of stress and the irreversible strain, which is defined as an internal state variable. The method for determining the model parameters is proposed. The creep model, along with the method of parameter determination, is validated using the test data from this study and literatures. The effect of strain rate on initial creep state is discussed using the model. The results provide a theoretical basis for understanding the transversely isotropic creep behaviors of rocks and enriching the basic theory of rock mechanics.