The damage and failure state of the loaded coal and rock masses is indirectly reflected by its acoustic emission (AE) characteristics. Therefore, it is of great significance to study the AE evolution of loaded coal and rock masses for the evaluation of damage degree and prediction of collapse. The paper mainly represents a numerical simulation investigation of the AE characteristics of coal specimen subjected to cyclic loading under three confining pressures, loading-unloading rates, and valley stresses. From the numerical simulation tests, the following conclusions can be drawn: (1) The final cycle number of coal specimen subjected to cyclic loading is significantly influenced by the confining pressure, followed the valley stress. With the increase in confining pressure or valley stress, the cycle number tends to increase. However, the loading-unloading rate has a little influence on it. (2) The AE counts of coal specimen subjected to cyclic loading are greatly influenced by the confining pressure and the valley stress. With the increase in the confining pressure, the cumulative AE counts at the 1st cycle tend to increase but decrease at a cycle before failure; with the decrease in the valley stress, the cumulative AE counts per cycle increase in the relatively quiet phase. However, the loading-unloading rate has a little influence on it. (3) The failure mode of coal specimen subjected to cyclic loading is significantly influenced by the confining pressure. Under the uniaxial stress state, there is an inclined main fractured plane in the coal specimen, under the confining pressures of 5 and 10 MPa, the coal specimen represents dispersion failure. The loading-unloading rate and valley stress have little influence on it. (4) The AE ratio is proposed, and its evolution can better reflect the different stages of coal specimen failure under cyclic loading. (5) The influence of confining pressure on the broken degree of coal specimen subjected to cyclic loading is analyzed, and the higher the confining pressure, the more broken the failed coal specimen.

中文翻译：

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循环载荷作用下煤样品的声发射模拟

加载的煤和岩体的破坏和破坏状态通过其声发射（AE）特性间接反映出来。因此，研究含煤岩体的声发射演化对损伤程度的评估和坍塌的预测具有重要意义。本文主要是对煤在三个约束压力，装卸速率和谷底应力下循环加载的声发射特性进行数值模拟研究。从数值模拟试验可以得出以下结论：（1）围压对煤样品的最终循环次数有明显的影响，其极限应力随谷值应力而变化。随着围压或谷应力的增加，循环次数趋于增加。然而，装卸速度对其影响不大。（2）围压和谷应力极大地影响了循环荷载作用下煤样品的AE数量。随着围压的增加，在第一个周期的累积AE计数趋于增加，而在失效前的一个周期减少。随着谷底应力的降低，相对安静阶段每个周期的累积AE计数增加。但是，装卸速度对其影响不大。（3）围压对煤样的破坏模式有很大的影响。在单轴应力状态下，煤样中存在一个倾斜的主断裂面，在5和10 MPa的围压下，煤样表现出分散破坏。装卸速率和谷底应力对其影响不大。（4）提出了AE比，其演化可以更好地反映循环荷载作用下煤样破坏的不同阶段。（5）分析了围压对循环荷载作用下煤样破坏程度的影响，围压越高，破坏的煤样破坏越多。