Many different practical constitutive models have been proposed for saturated fractured porous media, where the number of model parameters equals the number of constitutive state variables. However, none has considered the fully coupled deformation and hydromechanical behavior between pore and fracture domains. To address this issue, first, composite effective stresses are proposed as stress state variables based on the mixture theory, the nesting idea and the symmetrical formal role of pores and fractures. These variables can consider the interaction between the pore and fracture domains. Second, composite skeleton strains, which are energy-conjugate to the composite effective stresses, are derived from the first law of thermodynamics. Assuming the strain state variable solely depends on its conjugate stress state variable, the linear isotropic elastic equations of solid are derived by free energy potential function. The constitutive equations of fluid are derived using mass conservation equations and the constitutive equations of composite skeleton. Third, the approaches for measuring parameters of the model are introduced from the experiments on intact rock and joints, separately. Finally, the developed constitutive equations are compared theoretically and numerically with the Wilson & Aifantis model and the Khalili & Valliappan model. A parameters sensitivity analysis of the model is then conducted. The modelling results show that there are some differences in the initial fluid pressure magnitude, dissipation patterns, and final settlement of the model proposed in this paper compared to the other two models. Increasing permeability ratio facilitates a faster dissipation rate of fluid pressure in both pores and fractures, enhancing the consolidation rate of the rock mass. Increasing the shape factor facilitates the dissipation of pore fluid pressure and promotes settlement within a specific range.

中文翻译：

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考虑孔隙与裂隙域完全耦合的实用饱和裂隙多孔岩体本构模型


针对饱和裂缝多孔介质，人们提出了许多不同的实用本构模型，其中模型参数的数量等于本构状态变量的数量。然而，没有人考虑孔隙和裂缝域之间的完全耦合变形和流体力学行为。为了解决这个问题，首先，基于混合理论、嵌套思想以及孔隙和裂缝的对称形式作用，提出复合有效应力作为应力状态变量。这些变量可以考虑孔隙和裂缝域之间的相互作用。其次，复合材料骨架应变与复合材料有效应力能量共轭，源自热力学第一定律。假设应变状态变量仅取决于其共轭应力状态变量，则由自由能势函数推导出固体的线性各向同性弹性方程。利用质量守恒方程和复合骨架本构方程推导了流体本构方程。第三，分别从完整岩石和节理的实验中介绍了模型参数的测量方法。最后，将所开发的本构方程与 Wilson & Aifantis 模型和 Khalili & Valliappan 模型进行了理论和数值比较。然后进行模型的参数敏感性分析。建模结果表明，本文提出的模型与其他两个模型相比，在初始流体压力大小、耗散模式和最终沉降方面存在一定差异。 渗透率的增加有利于孔隙和裂隙中流体压力的消散速度加快，从而提高岩体的固结速度。增大形状系数有利于孔隙流体压力的消散，促进一定范围内的沉降。