Abstract Coal and gas outbursts have long posed a serious risk to safe and efficient production in coal mines. It is recognised that coal and gas outbursts are triggered by excavation unloading followed by gas-driven rapid propagation of a system of pre-existing or mining-induced fractures. Gas-filled fractures parallel to a working face are likely to experience opening first, then expansion and rapid propagation stages under unloading conditions. The fracture opening is driven by the effective stress inside the fracture, while the fracture expansion and rapid propagation is propelled by the pressure build-up of desorbed gas in the vicinity of the fracture. Based upon this understanding, this research aimed to identify the key factors affecting outburst initiation and its temporal evolution during roadway developments. Specifically, the response of pre-set fractures in a thin coal seam sandwiched between rock layers to roadway development is simulated using a geomechanical model coupled with fracture mechanics for fracture opening and propagation. In addition, kinetic gas desorption and its migration into open fractures is considered. During simulations outburst is deemed to occur when the fracture length exceeds the dimension of a host element. The findings of this research suggest that the simulated coal and gas outburst caused by roadway development may be considered as a dynamic gas desorption-driven fracture propagation process. The occurrence of coal and gas outbursts is found to be influenced mainly by the coal properties, fracture attributes, and initial gas pressure and the in situ stress conditions. Furthermore, the model predictions in terms of dome-shaped erupted-zone and layer-by-layer coal breakage are consistent with the field reports. In addition, the model results suggest that delayed occurrence of coal and gas outbursts, especially after sudden exposure of a coal seam or after blasting disturbance, reported in the literature may be related to the gas desorption behaviour.

中文翻译：

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煤与瓦斯突出卸荷条件下气体驱动裂缝快速扩展

摘要 煤与瓦斯突出长期以来对煤矿安全高效生产构成严重威胁。众所周知，煤和瓦斯突出是由挖掘卸载触发的，然后是由气体驱动的预先存在或采矿引起的裂缝系统的快速传播。与工作面平行的充气裂缝在卸载条件下可能先经历张开，然后是膨胀和快速扩展阶段。裂缝张开是由裂缝内部的有效应力驱动的，而裂缝扩展和快速扩展是由裂缝附近解吸气体的压力积聚推动的。基于这一认识，本研究旨在确定影响巷道开发过程中爆发发生及其时间演变的关键因素。具体来说，使用地质力学模型结合断裂力学模型来模拟夹在岩层之间的薄煤层中的预设裂缝对巷道发展的响应，用于裂缝张开和扩展。此外，还考虑了动力气体解吸及其向开放裂缝的迁移。在模拟过程中，当裂缝长度超过主体元素的尺寸时，就认为发生了爆发。研究结果表明，由巷道开发引起的模拟煤和瓦斯突出可以被认为是一个动态的瓦斯解吸驱动的裂缝扩展过程。发现煤与瓦斯突出的发生主要受煤的性质、裂缝属性、初始瓦斯压力和地应力条件的影响。此外，模型对圆顶状喷发带和逐层碎煤的预测与现场报道一致。此外，模型结果表明，煤和瓦斯突出的延迟发生，特别是在煤层突然暴露或爆破扰动之后，文献中报道可能与瓦斯解吸行为有关。