In deep underground engineering, true triaxial compressive stress and internal microcrack characteristics significantly influence the brittle-ductile transition and anisotropic mechanical behavior of rock, thereby affecting the engineering life cycle. However, current research on the micro-macro mechanical model under true triaxial compressive stress, particularly regarding the rock's brittle-ductile transition and anisotropic damage, is extremely limited. This paper aims to propose a macro-micromechanical model to describe the aforementioned physical and mechanical properties of rocks. The model introduces a lateral stress function into the micro-macro damage formula and derives the axial stress-strain relationship during crack propagation by incorporating the stress-crack length relationship under true triaxial stress. By considering the stress effects on the effective elastic modulus and nominal Poisson's ratio, the lateral stress-strain relationship is derived, resulting in a complete stress-strain curve. Finally, based on the relationships between triaxial principal strains, elastic deformation and triaxial principal stresses, the relationships between rock volumetric strain, crack volumetric strain, and triaxial principal stress are separately established. The influence of lateral principal stress on characteristic stresses is analyzed. The resulting model is combined with the brittleness evaluation index and the residual elastic energy index, respectively, to analyze the effects of micro parameters and principal stresses on brittleness and rockburst proneness. A comparative analysis of the similarities and differences between brittleness and rockburst proneness is conducted, revealing a positive correlation between the ratio of residual elastic energy and the post-peak to pre-peak brittleness index, expressed as CEF∝Bi2/Bi1. The proposed model theoretically addresses the issues of brittle-ductile transition and anisotropic damage under true triaxial conditions. It can also be applied to explain and predict rockburst proneness.

中文翻译：

---

用于评估真实三轴压缩下岩石脆性-韧性过渡和岩爆的微观-宏观断裂模型


在深部地下工程中，真正的三轴压应力和内部微裂纹特性显著影响岩石的脆性-韧性过渡和各向异性力学行为，从而影响工程生命周期。然而，目前对真三轴压应力下的微观-宏观力学模型的研究，特别是关于岩石的脆性-韧性转变和各向异性损伤的研究，极为有限。本文旨在提出一个宏观微观力学模型来描述岩石的上述物理和力学性质。该模型在微观-宏观损伤公式中引入侧向应力函数，并通过结合真三轴应力下的应力-裂纹长度关系，推导了裂纹扩展过程中的轴向应力-应变关系。通过考虑应力对有效弹性模量和标称泊松比的影响，推导出横向应力-应变关系，从而得到完整的应力-应变曲线。最后，基于三轴主应变、弹性变形和三轴主应力之间的关系，分别建立了岩石体积应变、裂缝体积应变和三轴主应力之间的关系。分析了侧向主应力对特征应力的影响。将所得模型分别与脆性评价指数和残余弹性能指数相结合，分析微观参数和主应力对脆性和岩爆易发性的影响。 对脆性和岩爆倾向的异同进行了比较分析，揭示了残余弹性能与峰后与峰前脆性指数（以 CEF∝Bi2/Bi1 表示）之间的正相关关系。所提出的模型从理论上解决了真三轴条件下的脆性-韧性转变和各向异性损伤问题。它也可以用于解释和预测岩爆的易发性。