In this study, a rigorous constitutive model within the framework of thermodynamics is formulated to describe the coupling process between irreversible deformation and anisotropic damage of rock materials. The coupling effect is reflected based on the “two-surface” formulation. The plastic response is described by a yield function while the anisotropic damage is defined by a novel exponential damage criterion. In the proposed model, another feature lies in introducing parameters β and k in the proposed model to capture strain hardening/softening behaviors and brittle–ductile transition. The computational formulation scheme for the coupled model is deduced in detail by using return mapping algorithm. The validity of the coupled model is compared with the numerical simulation results and the experimental curves of the fine-grained sandstone, Beishan granite, and Jinping marble. The results indicate that the model can take into account the nonlinear mechanical behaviors of rock: coupling anisotropic damage and plasticity as well as brittle-ductile transition behaviors. Without loss of generality, the coupled model is versatile to describe the mechanical characteristics of rock materials.

中文翻译：

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岩石材料的耦合弹塑性各向异性损伤模型

本研究在热力学框架内建立了严格的本构模型来描述岩石材料的不可逆变形与各向异性损伤之间的耦合过程。耦合效应反映在“双表面”公式的基础上。塑性响应由屈服函数描述，而各向异性损伤由新的指数损伤准则定义。在所提出的模型中，另一个特征在于在所提出的模型中引入参数 β 和 k 来捕捉应变硬化/软化行为和脆-韧转变。利用返回映射算法详细推导出耦合模型的计算公式。将耦合模型的有效性与细粒砂岩的数值模拟结果和实验曲线进行了比较，北山花岗岩，金平大理石。结果表明，该模型可以考虑岩石的非线性力学行为：耦合各向异性损伤和塑性以及脆韧转变行为。不失一般性，耦合模型可用于描述岩石材料的力学特性。