Research on gas pre-drainage in coal roadway strips by combined ordinary drilling and directional drilling
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摘要: 针对采用单一顺层普通钻孔或定向钻孔预抽煤巷条带瓦斯时存在普通钻机施工长钻孔易偏离轨迹、定向钻机施工成本较高等问题,以青龙煤矿21601掘进工作面为研究背景,提出了采用普通钻孔和定向钻孔联合预抽煤巷条带瓦斯。数值模拟结果表明:单钻孔预抽瓦斯时,抽采初期钻孔终孔位置处钻孔轴向瓦斯压力等值线呈“V”形分布,随着抽采时间延长,瓦斯压力“V”形分布逐渐平滑;钻孔径向瓦斯压力以钻孔为中心呈环状依次向外递增;预抽93 d时的有效抽采半径达3.80 m;普通钻孔和定向钻孔可分别有效控制煤巷两帮15 m和煤巷掘进工作面前方200 m范围内瓦斯。现场应用结果表明:普通钻孔和定向钻孔联合预抽时,瓦斯抽采总量平均值为19.86×103 m3,瓦斯抽采体积分数平均值为53.5%,瓦斯抽采纯流量平均值为1.97 m3/min,瓦斯抽采混合流量平均值为3.68 m3/min,残余瓦斯含量小于8 m3/t,瓦斯抽采效果良好。Abstract: When single layered ordinary drilling or directional drilling are used in gaspre-drainage in coal roadway strips, the long boreholes easily deviate from the trajectory and the cost of directional drilling is high. With the case study of 21601 excavation working face of Qinglong coal mine, the method of gaspre-drainage in coal roadway strips by combined ordinary drilling and directional drilling is proposed to solve the above problems. Numerical simulation results show thatwhen extracting the gas by single drilling, the axial gas pressure contour of drill hole at the end position of drill hole in the early stage is "V" shaped distribution. As the extraction time increases, the "V" shaped distribution of gas pressure gradually smooths. The gas pressure in the radial direction of the borehole gradually increases outwards in a ring shape with the borehole as the center. The effective extraction radius reaches 3.80 m at 93 d of pre-drainage. The ordinarydrilling and directional drilling can effectively control the gas in the range of 15 m in front of the two sides of the coal roadway and 200 m in front of the coal working face respectively. Field application results show that when ordinary drilling and directional drilling are combined for pre-drainage, the average value of total gas extractionis 19.86×103 m3, the average gas extraction volume fraction is 53.5%, the average pure gas extraction flow is 1.97 m3/min, the average mixed gasextraction is 3.68 m3/min, and the residual gas content is less than 8 m3/t.The gas extraction effect is proved to be good.
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Key words:
- coal mining /
- gas extraction /
- coal roadway strip gas /
- coal and gas outburst /
- extraction drilling /
- gas pressure
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