Abstract To uncover the failure and instability mechanism of coal-rock combination under loading, it is very crucial to investigate crack development and energy evolution. In this work, the uniaxial compressive and Brazilian split tests of coal-rock combinations were first performed. Secondly, the corresponding numerical models were built using the UDEC-Trigon method. Based on numerical results, the number, length and macroscopic area of cracks during failure and instability were determined, and the crack development and energy evolution rules were analysed. The main conclusions were obtained as follows: 1) the stress thresholds of crack initiation and damage of coal-rock combination rose with the increasing height ratio of coal to rock. The maximum event count of acoustic emission (AE) appeared earlier than the peak strength; 2) the failure and instability of coal-rock combination occurred when crack propagation and connection in central coal exceeded the damage limit. The shear failure was dominant mechanical behaviour of coal with the ratio 9:1 of shear to tensile fractures. The cracks connection was presented as a shear failure surface with an inclination angle of 15°–30° in coal and a vertical tensile failure plane in rock; and 3) the energy evolution in coal-rock combination was described as follows: the larger the height ratio of coal to rock is, the higher the cumulative energy is, and the faster the speed of energy dissipation is, indicating the higher risk of rockburst triggered by failure and instability of coal-rock combination.

中文翻译：

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受力煤岩组合裂缝发育及能量演化数值研究

摘要 为了揭示煤岩组合体在荷载作用下的破坏和失稳机制，研究裂缝的发展和能量演化至关重要。在这项工作中，首先进行了煤岩组合的单轴压缩和巴西劈裂试验。其次，利用UDEC-Trigon方法建立了相应的数值模型。根据数值结果，确定了破坏和失稳过程中裂纹的数量、长度和宏观面积，并分析了裂纹的发展和能量演化规律。主要结论如下：1）煤岩组合体裂纹萌生和破坏的应力阈值随着煤岩高度比的增加而升高。声发射（AE）的最大事件计数出现早于峰值强度；2) 煤岩中部裂纹扩展与连接超过破坏极限时发生煤岩组合破坏和失稳。剪切破坏是煤的主要力学行为，剪切断裂与拉伸断裂之比为 9:1。裂缝连接表现为煤中倾角为15°～30°的剪切破坏面和岩石中的垂直拉伸破坏面；3) 煤岩组合能量演化描述为：煤岩高度比越大，累积能量越高，能量消散速度越快，表明发生岩爆的风险越高由煤岩组合的破坏和失稳引发。剪切破坏是煤的主要力学行为，剪切断裂与拉伸断裂之比为 9:1。裂缝连接表现为煤中倾角为15°～30°的剪切破坏面和岩石中的垂直拉伸破坏面；3) 煤岩组合能量演化描述为：煤岩高度比越大，累积能量越高，能量消散速度越快，表明发生岩爆的风险越高由煤岩组合的破坏和失稳引发。剪切破坏是煤的主要力学行为，剪切断裂与拉伸断裂之比为 9:1。裂缝连接表现为煤中倾角为15°～30°的剪切破坏面和岩石中的垂直拉伸破坏面；3) 煤岩组合能量演化描述为：煤岩高度比越大，累积能量越高，能量消散速度越快，表明发生岩爆的风险越高由煤岩组合的破坏和失稳引发。