Practice of gas drainage by high-level directional borehole in Qinglong Coal Mine
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摘要: 针对高位钻孔瓦斯抽采存在钻孔数量多、单孔深度不足、钻孔轨迹不可控、瓦斯抽采浓度较低、抽采不连续等问题,为有效防治青龙煤矿21602工作面回采期间上隅角瓦斯浓度超限,利用高位定向钻孔技术对瓦斯进行抽采,介绍了高位定向钻孔设计施工方案,通过现场实践确定了最佳钻孔布置参数。结果表明:高位定向钻孔具有瓦斯抽采浓度高、抽采量大、抽采率高等特点,且高位定向钻孔瓦斯抽采效果随工作面回采距离的增加呈先稳定后下降的趋势;当高位定向钻孔终孔层位距离顶板39 m、距离回风巷右帮水平位移为55 m时,瓦斯抽采体积分数达30.5%,瓦斯抽采流量达18 m3/min,瓦斯抽采纯量达2.374 m3/min,瓦斯抽采效果最佳;上隅角瓦斯体积分数由抽采前的最大值0.72%降低至抽采期间的0.2%~0.4%,有效解决了上隅角瓦斯浓度超限问题。Abstract: Aiming at problems of gas drainage by high-level borehole such as too many boreholes, insufficient single borehole depth, uncontrollable borehole trajectory, low gas drainage concentration and discontinuous drainage, in order to effectively prevent and control gas concentration overrunning in upper corner of 21602 mining face in Qinglong Coal Mine, gas drainage was carried out by use of high-level directional borehole technology. Design and construction schemes of high-level directional borehole were introduced, and the best borehole layout parameters were determined through field practice. The results show that high-level directional borehole has the characteristics of high gas drainage concentration, large drainage volume and high drainage rate, and gas drainage effect of high-level directional borehole tends to stabilize first and then decreases with the increase of mining distance. When the final hole of high-level directional borehole is 39 m away from roof and 55 m away from right side of return airway, gas drainage effect is the best with gas drainage volume fraction reaching 30.5%, gas drainage flow reaching 18 m3/min and gas drainage pure volume reaching 2.374 m3/min. Gas volume fraction in upper corner is reduced to the range from 0.2% to 0.4%, which is up to 0.72% before extraction. It effectively solves problem of gas concentration overrunning in upper corner.
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