In order to study the acoustic emission characteristics and Felicity effect in the process of coal fatigue failure and reveal the internal relationship between the fatigue damage evolution law and the acoustic emission activity, with the help of MTS815.02 electrohydraulic servo rock mechanics test system and PCI-2 acoustic emission detection and analysis system, a triaxial cycling loading acoustic emission test was carried out on the coal samples. The results show that the higher the upper limit stress is, the more obvious the degree of fatigue damage will be caused by coal samples. At the same time, the more active acoustic emission signal will appear. The coal samples under linear loading are on the initial damage state, and slight fatigue, moderate fatigue, deep fatigue, and ultimate fatigue failure under cyclic loading. The acoustic emission shows the “L-” type development evolution law in any previous stress level range, while at the last stress level, it shows the obvious “U-” type development evolution law. The higher the frequency of the cyclic loading is, the higher the rate of initiation and expansion of the microcrack will be, while the more obvious acoustic emission phenomenon will appear. Furthermore, the ringing counting rate is basically the same as that of the energy counting rate. Under triaxial cyclic loading, a shear failure mode that extends along different directions of fracture surface will be presented. The acoustic emission in the range of different stress levels shows a different degree of Felicity effect. In contrast, it is more reasonable to use the principal stress difference as a parameter to study the Felicity effect of coal under cyclic loading.

中文翻译：

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循环载荷作用下煤疲劳破坏声发射特性及有限元效应的实验研究

为了研究煤疲劳破坏过程中的声发射特性和费利斯效应，并借助MTS815.02电液伺服岩石力学测试系统和PCI，揭示了疲劳损伤演化规律与声发射活动之间的内在联系。 -2声发射检测与分析系统，对煤样进行了三轴循环加载声发射测试。结果表明，上限应力越高，煤样引起的疲劳损伤程度越明显。同时，将出现更活跃的声发射信号。线性载荷下的煤样处于初始破坏状态，循环载荷下轻度疲劳，中度疲劳，深度疲劳和最终疲劳破坏。声发射在任何先前的应力水平范围内均表现出“ L-”型发展演变规律，而在最后的应力水平上，其表现出明显的“ U-”型发展演变规律。周期性加载的频率越高，微裂纹的萌生和扩展的速率就越高，而声发射现象就会越明显。此外，振铃计数率与能量计数率基本相同。在三轴循环荷载作用下，将出现沿断裂面不同方向延伸的剪切破坏模式。在不同应力水平范围内的声发射表现出不同程度的费利西特效应。相反，