Using discrete element software, namely, particle flow code as two-dimensional program (PFC2D), two types of models were established: vertical fissure hole combination and horizontal fissure hole combination with ratios of major and minor axis of ellipse being 1, 1.2, 1.5, 2, and 3, which corresponded to a total of ten samples. The failure mode, mechanical behavior, and stress state before and after crack generation in elliptical hole crack combination models with different ratios of major and minor axis were analyzed. The crack development, stress field evolution, and acoustic emission characteristics of the vertical fissure model and horizontal fissure model were studied at the optimized ratio of major and minor axis of ellipse being 1.5. The results showed that elliptical hole fissure with different ratios of major and minor axis resulted in the decrease in the strength and elastic modulus of rock and increase in the peak strain of rock. The effect of the horizontal fissure model on the peak strength, peak strain, and elastic modulus of rock was found to be greater than that of the vertical fissure hole model. Ellipses with different ratios of major and minor axis in various models slightly influenced the rock failure modes, and their failure modes corresponded to tensile shear failure and tensile failure. Before crack formation, the tensile stress concentration areas of each model were, respectively, distributed at the upper and lower ends of the vertical fissure and the major axis of ellipse, and the compressive stress concentration areas were distributed at both ends of the major axis of ellipse and the fissure in the horizontal direction. After the model failed, the compressive stress concentration areas of the vertical fissure model and the horizontal fissure model transferred to the left upper part and the right upper part of the model along the left end of the hole and the right end of the fissure, respectively. When the ratio of major and minor axis of ellipse was 1.5, cracks in the vertical model and the horizontal model of fissure developed along the axial direction at the ends of cracks and holes, respectively, and then secondary cracks were generated at the ends of left and right sides. The maximum compressive stress in each stage of the vertical fissure model was greater than that of the horizontal fissure model, and when the model was damaged, its stress release was more.

中文翻译：

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裂隙缺陷岩石的强度，变形和破坏特性的数值模拟

使用离散元软件，即粒子流代码作为二维程序（PFC2D），建立了两种类型的模型：垂直裂缝孔组合和水平裂缝孔组合，椭圆长轴和短轴的比率分别为1、1.2、1.5 ，2和3，它们对应于总共十个样本。分析了长短轴比例不同的椭圆孔裂纹组合模型中裂纹产生前后的失效模式，力学行为和应力状态。以椭圆长轴和短轴的最佳比例为1.5时，研究了垂直裂缝模型和水平裂缝模型的裂纹发展，应力场演化和声发射特性。结果表明，长轴和短轴比率不同的椭圆孔裂隙导致岩石强度和弹性模量下降，岩石峰值应变增加。发现水平裂缝模型对岩石的峰值强度，峰值应变和弹性模量的影响要大于垂直裂缝孔模型的影响。在各种模型中，长轴和短轴比率不同的椭圆对岩石破坏模式的影响较小，其破坏模式分别对应于拉伸剪切破坏和拉伸破坏。在裂纹形成之前，每个模型的拉伸应力集中区域分别分布在垂直裂缝的上端和下端以及椭圆的长轴，压缩应力集中区域分布在椭圆长轴和裂缝的水平方向的两端。模型失效后，垂直裂缝模型和水平裂缝模型的压缩应力集中区域分别沿孔的左端和裂缝的右端转移到模型的左上部和右上部。当椭圆的长轴与短轴之比为1.5时，垂直裂缝模型和水平裂缝模型的裂缝分别在裂缝和孔的末端沿轴向方向发展，然后在裂缝的左端产生次要裂缝。和右侧。垂直裂缝模型各阶段的最大压应力大于水平裂缝模型的最大压应力，