In this paper, we shall present a new micromechanical damage model for capturing the mechanical behaviors of quasi-brittle geomaterials under a wide range of compressive stress. Two essential coupled non-linear mechanisms are taken into account: plastic deformation related to frictional sliding along the microcrack surfaces, and microscopic damage induced by the initiation and propagation of microcracks. Within the framework of thermodynamics and Mori–Tanaka homogenization scheme, free energy and thermodynamic forces, including the local stress applied on the microcracks and damage driving force are deduced. The main novelty of this work lies in presenting a new physically based non-associated and state-dependent friction law to capture the plastic distortion, in which the friction coefficient is no longer a constant but a state-dependent variable varying with the surface asperities of microcracks. The relationship between the friction coefficient and mean local stress, as well as microscopic damage is subtly defined. Intriguingly, a macroscopic strength criterion is derived as an inherent part of the proposed model without rotation of the principal stress. Moreover, semi-analytical stress–strain–damage relationships of the proposed model can be derived under conventional triaxial compression. These up-scaling analyses provide a powerful tool for parameter calibration. For application, the semi-implicit return mapping algorithm with plasticity-damage decoupling correction procedure (SRM-PDDC) is adopted for numerical implementation. To demonstrate the performance of the micromechanical model, we compare the model predictions with experimental data of quasi-brittle rocks in literature as well as the results obtained by Zhu et al. (2016). Finally, the applicable condition of the SRM-PDDC algorithm is discussed in detail.

在本文中，我们将提出一种新的微观机械损伤模型，用于捕捉准脆性岩土材料在大范围压应力下的力学行为。考虑了两个基本的耦合非线性机制：与沿微裂纹表面的摩擦滑动相关的塑性变形，以及由微裂纹的萌生和传播引起的微观损伤。在热力学和 Mori-Tanaka 均匀化方案的框架内，推导出自由能和热力学力，包括施加在微裂纹上的局部应力和损伤驱动力。这项工作的主要新颖之处在于提出了一种新的基于物理的非关联和状态依赖摩擦定律捕捉塑性变形，其中摩擦系数不再是常数，而是随微裂纹表面粗糙度变化的状态相关变量。摩擦系数与平均局部应力以及微观损伤之间的关系被巧妙地定义。有趣的是，在没有主应力旋转的情况下，导出了宏观强度准则作为所提出模型的固有部分。此外，可以在常规三轴压缩下推导出所提出模型的半解析应力-应变-损伤关系。这些放大分析为参数校准提供了强大的工具。对于应用，具有塑性损伤解耦校正程序的采用（SRM-PDDC）进行数值实现。为了证明微观力学模型的性能，我们将模型预测与文献中准脆性岩石的实验数据以及 Zhu 等人获得的结果进行了比较。(2016)。最后详细讨论了SRM-PDDC算法的适用条件。