Goaf gas drainage is extensively employed in Australian gassy underground coal mines to manage safety and productivity and to mitigate gas emissions. As mining operations reach greater depths and produce higher levels of gas emissions, narrower spacing between adjacent vertical goaf boreholes and higher suction pressure are increasingly being adopted. While this proactive goaf gas drainage design enhances gas extraction efficiency, there is a concern that an increased amount of ventilation air might be drawn back into the deep goaf, potentially resulting in the formation of an explosive gas zone (EGZ) composed of methane-air mixtures. Extensive goaf gas drainage data from various Australian coal mines have undergone detailed analysis in preceding back analysis studies (Wang et al., 2022a, 2023). These findings serve as crucial validation input for a CFD model of the goaf, providing ventilation engineers with visualization of an otherwise inaccessible environment. In this paper, the simulation outcomes of the CFD model were integrated with Coward's triangle to demarcate potential EGZ within the active goaf areas. It indicated that the EGZ was pushed far away from the longwall face under the impact of intensive goaf gas drainage compared to the EGZ without the active goaf boreholes, exhibiting a ‘U-shaped’ distribution. Furthermore, this study delves into the gas drainage factors influencing EGZs in the goaf, emphasising the impact of various gas drainage designs on gas explosion risks within the goaf. Factors such as the number of active boreholes and completion depth are assessed, with the size of EGZ serving as a quantitative evaluation criterion. Therefore, this paper plays a pivotal role in optimising goaf gas drainage efficiency, striving to minimise gas emissions into the atmosphere while upholding the priority of mining and worker safety.

中文翻译：

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地面垂直钻孔采空区瓦斯抽采对采空区爆炸性瓦斯区的影响

澳大利亚瓦斯地下煤矿广泛采用采空区瓦斯抽放，以管理安全和生产力并减少瓦斯排放。随着采矿作业深度越来越深，瓦斯排放量越来越高，越来越多地采用相邻垂直采空区钻孔之间更窄的间距和更高的抽吸压力。虽然这种主动采空区瓦斯抽采设计提高了瓦斯抽采效率，但人们担心更多的通风空气可能会被抽回到采空区深处，可能导致形成由甲烷-空气组成的爆炸性气体区（EGZ）混合物。在之前的回溯分析研究中，对澳大利亚各煤矿的大量采空区瓦斯抽放数据进行了详细分析（Wang 等，2022a，2023）。这些发现是采空区 CFD 模型的重要验证输入，为通风工程师提供了原本无法进入的环境的可视化。在本文中，CFD 模型的模拟结果与 Coward 三角相结合，以划分活动采空区内的潜在 EGZ。这表明，与没有活动采空区钻孔的EGZ相比，在强烈的采空区瓦斯抽采影响下，EGZ被推离长壁工作面较远，呈现“U”形分布。此外，本研究还深入探讨了影响采空区EGZ的瓦斯抽采因素，强调了各种瓦斯抽采设计对采空区瓦斯爆炸风险的影响。评价活动钻孔数量、完井深度等因素，以EGZ大小作为定量评价标准。因此，本文对于优化采空区瓦斯抽采效率、努力最大限度地减少瓦斯排放到大气中、同时坚持采矿和工人安全优先具有关键作用。