Open flaws without any filling material are common fracture structures in real rock. To study the failure characteristics of this fracture structure, small-scale rock-like samples with single internal 3D open flaws are prepared, and uniaxial compression tests are conducted. Digital image correlation (for surface strain and failures) and acoustic emission (for internal microfracture behaviors) monitoring technologies are also employed to analyze the flaws. The test results are verified through numerical simulations. Different inclination angles of the internal preset flaws are found to have little influence on the strength of the samples, and the surface and internal secondary failures of the samples exhibit very different development processes and distributions. The particle displacement trend method is applied to explain the initiation mechanism of secondary cracks, but the corresponding analyses are only reasonable if particle information along the y-axis is considered. Therefore, the particle information in the y-axis is incorporated by defining new 2D sections (with y-axis) or partial 3D models. Based on these research methods, the initiation mechanism of secondary cracks is reasonably explained, and the influence of the preset flaw thickness on the particle displacement trend fields and secondary failures in surrounding rocks can be discussed. Finally, the simulation results prove that the Mode II and III failures are usually coupled, and direct Mode III failures (displacement of two parts of rock parallel to each other and in opposite directions) only occur in the front and rear surrounding rocks of the preset flaw.

没有任何填充材料的开放缺陷是真实岩石中常见的断裂结构。为研究该断裂结构的破坏特征，制备了具有单一内部3D开放缺陷的小型类岩石样品，并进行了单轴压缩试验。数字图像相关（用于表面应变和故障）和声发射（用于内部微裂纹行为）监测技术也用于分析缺陷。试验结果通过数值模拟得到验证。发现内部预置缺陷的不同倾角对试样的强度影响不大，试样的表面和内部二次破坏的发展过程和分布有很大差异。应用粒子位移趋势法来解释二次裂纹的萌生机理，但只有考虑沿y轴的粒子信息，相应的分析才是合理的。因此，通过定义新的 2D 截面（带有 y 轴）或部分 3D 模型来合并 y 轴中的粒子信息。基于这些研究方法，合理解释了二次裂纹的萌生机理，探讨了预设裂纹厚度对围岩颗粒位移趋势场和二次破坏的影响。最后，仿真结果证明模式 II 和 III 故障通常是耦合的，