The existing cracks in the roof rock are critical to stability of the coal-rock combination structure during mining activities, which is vital for safe exploitation in coal mines. However, the physical mechanisms by which pre-existing crack in the roof rock induces rockburst in coal mines are still poorly understood. In this study, to investigate the rockburst characteristics in an underground mine, triaxial compressive experiments on coal-rock combinations containing a pre-existing crack in the roof rock were carried out. Both mechanical and failure behaviours of composite specimen containing a pre-existing crack were analysed. The testing results showed that a pre-existing crack in roof significantly affects mechanical properties of combinations. The average peak stress and average elastic modulus of specimen exhibit an M-shaped change trend when dip angle is in a range of 0°–90°. The average peak strain increases before decreasing with increase in dip angle. In addition, the roof rock is more likely to fail when it contains a pre-existing crack. Both the initial failure location and failure pattern of combinations are highly related to angle of pre-existing crack. A novel rockburst model considering in-situ stress and pre-existing crack was proposed to determine the physical mechanism of rockburst. The findings are useful to understand characteristics and physical mechanism of rockburst in mine engineering.

中文翻译：

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煤岩组合体中预存裂缝对岩爆特性的影响：室内研究

顶板岩石中存在的裂缝对于采矿活动中煤岩组合结构的稳定性至关重要，对煤矿的安全开采至关重要。然而，对于煤矿顶板岩石中预先存在的裂缝引起岩爆的物理机制仍然知之甚少。在这项研究中，为了研究地下矿井的岩爆特征，对顶板岩石中含有预先存在的裂缝的煤岩组合进行了三轴压缩试验。分析了含有预先存在的裂纹的复合材料样品的机械和失效行为。测试结果表明，屋顶预先存在的裂缝会显着影响组合的力学性能。当倾角在0°~90°范围内时，试件的平均峰值应力和平均弹性模量呈现M形变化趋势。随着倾角的增大，平均峰值应变先增大后减小。此外，当顶板岩石包含预先存在的裂缝时，顶板岩石更有可能失效。组合的初始失效位置和失效模式都与预存裂纹的角度高度相关。提出了一种考虑地应力和预存裂纹的新型岩爆模型来确定岩爆的物理机制。研究结果有助于了解矿山工程岩爆的特征和物理机制。