To effectively control and utilise large amounts of gas emissions from underground coal mining, Australia and many other countries rely heavily on a series of vertical boreholes to capture the gas during mining. This gas capture not only reduces the greenhouse gas impact but also recovers a significant amount of energy. Vacuum pumps are connected to surface boreholes to drive gas flow from the goaf and overlying fractured strata. However, applying high suction pressure to the boreholes may cause more oxygen to enter the goaf from the longwall working face. This influx of oxygen can potentially react with residual coal in the goaf, accelerating coal self-heating and possibly resulting in endogenous fires. By analysing extensive goaf gas drainage data collected from Australian longwalls, researchers have established the normal trend of goaf gas concentration and flow rate as a result of intensive goaf gas drainage. This paper further developed goaf gas flow CFD models with the operating vertical boreholes, which were then calibrated using field borehole production data under certain operating conditions. The CFD model simulated the distribution of O₂ and CH₄ as well as the gas flow pathways in the goaf, considering the complication of goaf gas drainage. This study found that the O₂ concentration is higher on the goaf tailgate side under the influence of tailgate side boreholes compared to the maingate side. Furthermore, for the well-compacted goaf, a significant proportion of the ventilation air travels through ‘high permeability flow channels’ provided by the goaf edge on tailgate side, and then circulates back into the goaf boreholes. These CFD modelling results not only enable ventilation engineers to visualize the goaf gas flow patterns under the impact of multiple operating boreholes, but also to understand the impact on goaf atmosphere through sensitivity analysis of natural goaf characteristics, such as goaf permeability distributions and gas emission rates.

为了有效控制和利用地下煤矿开采产生的大量瓦斯排放，澳大利亚和许多其他国家在采矿过程中严重依赖一系列垂直钻孔来捕获瓦斯。这种气体捕获不仅减少了温室气体的影响，而且还回收了大量的能源。真空泵连接到地面钻孔，以驱动采空区和上覆裂隙地层的气流。然而，向钻孔施加高抽吸压力可能会导致更多的氧气从长壁工作面进入采空区。氧气的流入可能会与采空区中残留的煤炭发生反应，加速煤炭自热，并可能导致内生火灾。通过分析从澳大利亚长壁收集的大量采空区瓦斯抽采数据，研究人员确定了采空区集约瓦斯抽采导致的采空区瓦斯浓度和流量的正常趋势。本文进一步开发了具有作业垂直钻孔的采空区瓦斯流动CFD模型，然后使用特定作业条件下的现场钻孔生产数据进行校准。CFD模型考虑了采空区瓦斯抽采的复杂性，模拟了采空区O ₂和CH ₄的分布以及瓦斯流动路径。本研究发现，在尾门侧钻孔的影响下，与主门侧相比，采空区尾门侧的O _{2浓度较高。}此外，对于压实良好的采空区，很大一部分通风空气通过后挡板侧采空区边缘提供的“高渗透性流动通道”，然后循环回到采空区钻孔。这些CFD建模结果不仅使通风工程师能够可视化在多个作业钻孔影响下的采空区气体流动模式，而且还可以通过对采空区渗透率分布和瓦斯排放率等自然采空区特征的敏感性分析来了解对采空区大气的影响。