In this paper, the microscopic mechanism of crack evolution in brittle material containing 3-D embedded flaw is investigated. The crack evolution mode of 3-D flaw is summarized by the uniaxial compression experiment first. Based on experiment results, the micro-parameters in the flat-joint model are calibrated and numerical models containing 3-D embedded flaw are established in PFC3D. Then, the numerical uniaxial compression experiment is carried out to validate the effectiveness of numerical model. The simulation results indicate that the flat-joint model is appropriate to model the cracking processes of 3-D flaw. The method of particle velocity vector field is introduced to analyze crack evolution mechanism, and four types of particle velocity vector field corresponding to typical cracks are proposed. Generally, the initiation of wing crack is tensile crack and the further propagation is mixed tensile and shear crack. However, the interaction between flaws has important impacts on the crack evolution mechanism and the specimen failure mode. In the rock bridge, wing crack may initiate as mixed tensile and shear crack. The failure mode turns from burst failure to splitting failure with the condition changing from single flaw to double flaws.

中文翻译：

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含3-D嵌入缺陷脆性材料裂纹演化的微观机制

本文研究了含3-D嵌入缺陷的脆性材料裂纹演化的微观机制。首先通过单轴压缩实验总结了三维裂纹的裂纹演化模式。根据实验结果，在PFC3D中校准平接头模型中的微观参数并建立包含3-D嵌入缺陷的数值模型。然后，通过数值单轴压缩实验验证了数值模型的有效性。仿真结果表明，平接头模型适用于模拟 3-D 裂纹的开裂过程。引入粒子速度矢量场方法分析裂纹演化机理，提出了四种典型裂纹对应的粒子速度矢量场。一般来说，翼裂纹的起始为拉伸裂纹，进一步扩展为拉伸和剪切混合裂纹。然而，缺陷之间的相互作用对裂纹演化机制和试样破坏模式有重要影响。在岩桥中，翼状裂纹可能以拉剪混合裂纹的形式萌生。失效模式由爆裂失效转为分裂失效，状态由单裂纹变为双裂纹。