煤层瓦斯抽采失效钻孔管底二次注浆技术研究

Study on secondary grouting technology for coal seam gas extraction failure in borehole pipe bottom

为解决失效钻孔漏气导致抽采瓦斯浓度降低的问题,根据钻孔内、外漏气机理,分析得到孔外漏气受钻孔轴向巷道煤壁破碎漏气带和钻孔径向围岩漏气圈的影响,孔内漏气区域分布受封孔材料漏气阻力系数、封孔段长度、支护强度等多重因素的影响,提出对失效钻孔进行靶向二次注浆的思路。阐述了失效钻孔管底二次注浆提浓技术,根据检测出的瓦斯浓度变化趋势分析得出钻孔具体漏气区域,从而确定钻孔需要二次封堵注浆的具体位置与长度;通过注浆专用设备,将浆液注入漏气钻孔封孔段附近的漏气通道中,随着浆液在贯通裂隙中流动、充填、凝固,钻孔通道被封堵,孔外空气进入孔内的阻力增大或无法进入孔内,实现对漏气通道的靶向处理。研发了钻孔漏气位置检测及管底二次注浆提浓装备,主要由封孔气囊、双通道连接管、孔口三通等部件组成;结合山西某矿S5101采煤工作面现有钻孔的实际尺寸情况,对装置整体尺寸进行设计;选用KFGP-Ⅲ型微膨胀水泥基瓦斯封孔专用材料,并对其材料性能、外加剂和浆液配合比进行试验。通过模拟验证了管底二次注浆的有效性,模拟结果表明钻孔周边裂隙和一次封孔段收缩失效形成的漏气通道在管底二次注浆条件下得到了有效封堵。在余吾煤业进行工业性试验,试验钻孔注浆后瓦斯抽采体积分数总体提升至35%~80%,试验数据表明注浆后不仅对试验钻孔提浓效果明显,对注浆钻孔邻近范围内的抽采钻孔瓦斯浓度同样具有一定提升作用。

In order to solve the failure results in the decrease of gas concentration extraction hole leakage problems, according to the mechanism of internal and external leakage, borehole outside air leakage can be gained by analyzing the borehole axial wall broken flat belt and radial borehole surrounding rock of roadway coal gas leakage circle of influence, regional distribution of hole leakage hole sealing material leakage resistance coefficient, hole sealing length, the influence of multiple factors such as support strength, for failure of drilling was targeted secondary grouting. The technology of secondary grouting at the bottom of the failed drilling pipe is described. According to the variation trend of detected gas concentration, the specific leakage area of the borehole is obtained, and the specific location and length of the borehole that needs secondary grouting are determined. The special grouting equipment is used to inject the grout into the leakage passage near the sealing section of the leakage borehole. With the flow, filling and solidification of the grout in the penetrating crack, the borehole passage is blocked, and the resistance of the air outside the hole to enter the hole increases or it cannot enter the hole, so as to realize the targeted treatment of the leakage passage. The equipment for detecting the location of the hole leakage and the secondary grouting and thickening at the bottom of the pipe has been developed, which is mainly composed of sealing air bag, double-channel connecting pipe,orifice tee and other components. Combined with the actual size of the existing drilling holes in the S5101 mining face of a mine in Shanxi,the overall size of the device is designed. KFGP-Ⅲ micro-expansion cement-based special material for gas hole sealing is selected, and its material properties, admixtures and grout ratio were tested. The effectiveness of the secondary grouting at the bottom of the pipe is verified by simulation. The simulation results show that the leakage channels formed by the cracks around the borehole and the shrinkage failure of the primary sealing section are effectively blocked under the condition of the secondary grouting at the bottom of the pipe. Industrial tests were carried out in Yuwu Coal Industry, and the concentration of the test borehole was generally increased to 35% ~80% after grouting. The test data showed that the grouting not only significantly enhanced the concentration of the test borehole, but also improved the gas concentration of the drainage borehole within the adjacent range of the grouting borehole to a certain extent.