Sectional hydraulic reaming technology has been widely used in China; however, because of the lack of research on mechanisms that reduce coal seam stress, improve air permeability, and promote methane extraction, on-site construction parameters are mostly determined from experience, and the effect is often not ideal. In this study, a stress-damage-flow coupling model for methane extraction was established, and a numerical simulation method was used to analyze the effects of the size and spacing of hydraulic flushing cavities on the pressure relief and permeability of a coal seam. The results showed that the cavities produced by sectional hydraulic reaming have an interactive effect that effectively reduces the stress and increases the permeability of the coal seam. The greater the radius of the cavity, the wider the development range of the stress reduction area and the higher the degree of pressure relief. The greater the increase in permeability, the better the coal seam methane extraction effect under the same extraction conditions. For the same cavity radius, the longest distance of the stress reduction zone was unchanged. The lower the distance between two hydraulic flushing cavities, the more evident the superimposing effect they produced and the wider the pressure relief range of the coal seam. In contrast, when their distance was considerable, there was no superposition effect; this significantly reduced the efficiency of the hydraulic flushing cavities in increasing the permeability of the coal seam. In Gaohe Mine, if the distance between two hydraulic flushing cavities is > 7 m, the superposition effect will disappear. This research provides a theoretical basis for better field application of sectional hydraulic reaming technology.

分段液压铰孔技术在国内已得到广泛应用；但由于缺乏对降低煤层应力、提高透气性、促进瓦斯抽采的机理研究，现场施工参数多凭经验确定，效果往往不理想。本研究建立了瓦斯抽采应力-损伤-流耦合模型，采用数值模拟方法分析了水力冲洗腔的大小和间距对煤层卸压和渗透率的影响。结果表明，分段水力扩孔产生的空腔具有交互作用，有效降低了煤层的应力，提高了煤层的渗透率。腔体半径越大，减压区的发展范围越广，减压程度越高。渗透率增加的越大，相同提取条件下煤层气提取效果越好。对于相同的腔半径，应力降低区的最长距离不变。两个水力冲洗腔之间的距离越小，它们产生的叠加效果越明显，煤层的卸压范围越宽。相比之下，当它们的距离相当大时，则没有叠加效应；这显着降低了液压冲洗腔在增加煤层渗透性方面的效率。在高河矿，如果两个水力冲洗腔之间的距离> 7 m，叠加效应就会消失。