下保护层开采高位钻孔瓦斯抽采规律的三维数值分析及应用

为了事先确定下保护层开采时不同钻孔层位的抽放效果，构建了包含3种不同高低位置钻孔的三维采场模型。利用FLUENT软件求解渗流扩散方程得到了"Y"型通风工作面采空区瓦斯的空间分布情况，并对不同位置钻孔抽放效果进行比较。结果表明:两个进风巷附近瓦斯浓度最低，沿走向瓦斯浓度向采空区深部逐渐升高，瓦斯整体有上浮趋势，在据工作面后沿空留巷侧上部积聚大量高浓度瓦斯。高位穿层钻孔周围瓦斯浓度降低明显，抽放浓度和影响范围优于低位钻孔。经立体抽采后，留巷处附近瓦斯富集区范围缩小，瓦斯重新分布效应明显。研究结论同现场监测记录保持一致，具有类似近距离下保护层开采工作面，应考虑以高位钻孔为主的抽放布局。 

Application of three-dimensional numerical simulation for law of gas drainage through high-level boreholes in lower protective coal seam

Aiming at inferring the drainage effects of boreholes at different horizons under low protective coal seam, the 3D stope model including three kinds of boreholes was established and FLUENT was used to solve seepage and diffusion equation for gaining methane distribution of "Y" ventilation face in space and the drainage effects of boreholes at different position was compared. The results showed that the gas concentration was the lowest near two intake airways and increased along the depth of goaf. Besides, gas tended to float upward on the whol, and a lot of gas of high concentration was accumulated in the upper of the entry at the back of face. Finally, around high level crossing hole which had better drainage effects and large control scope, the gas concentration decreased evidently. Through the stereoscopic drainage with all drill holes, the gas-riched area above goaf became smaller, and the effect of gas redistribution was obvious. The research conclusion accords with monitoring record in site, hence for the working face which has similar near-distance low protective coal seam, the high level hole should be considered as main drainage pattern.