The aim of this study was to develop a systematic method to analyze the rock failure mechanism under stress unloading conditions. In this method, three types of basic tests (Brazilian splitting, direct shear, and three-point bending) were used to extract acoustic emission (AE), dissipative energy, and fracture parameters to analyze the failure mechanism under stress unloading. The key parameters are as follows: the critical slope in rise time/amplitude—average frequency (RA-AF) coordinate system; the dissipation energy (u_s and u_t) of unit shear and tensile cracks; relative roughness (δ) of fracture—variation coefficient of gray value of digital image for fracture. Additionally, the effectiveness of this method was illustrated by a rock burst experiment. The results show that most (92.3%) of the fragments during rock burst were produced by tension, while the energy consumed by shear cracks is ~ 1.03 times of tensile cracks. Moreover, the density of AE events is negatively correlated with the amount of released energy. Furthermore, the tensile microcracks concentrated as a splitting zone after yielding but before burst. However, in the burst stage, the shear microcracks breakthrough to form a shear zone, while the elastic strain energy released was partially transformed into kinetic energy to form the ejection zone. In addition, for the dissipation energy, the energy consumptions by shear, tension, and plastic deformation account for 62.5%, 25.2%, and 12.3%, respectively.

中文翻译：

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应力卸载条件下岩石破坏机理的系统分析方法：以岩爆为例

这项研究的目的是开发一种分析应力卸载条件下岩石破坏机理的系统方法。在这种方法中，使用三种类型的基础测试（巴西劈裂，直接剪切和三点弯曲）提取声发射（AE），耗散能和断裂参数，以分析应力卸载下的破坏机理。关键参数如下：上升时间/幅度-平均频率（RA-AF）坐标系的临界斜率；单位剪切裂纹和拉伸裂纹的耗散能量（u _s和u _t）；相对粗糙度（δ）-断裂数字图像灰度值的变异系数。此外，通过岩爆实验证明了该方法的有效性。结果表明，岩石破裂过程中的大部分碎片（92.3％）是由张力产生的，而剪切裂缝所消耗的能量约为拉伸裂缝的1.03倍。此外，AE事件的密度与释放的能量负相关。此外，拉伸微裂纹在屈服之后但在破裂之前集中为分裂区域。然而，在破裂阶段，剪切微裂纹突破以形成剪切区，而释放的弹性应变能被部分转化为动能以形成喷射区。另外，对于耗散能量，通过剪切，拉伸，