【摘要】 针对留巷钻孔受采动影响大、破坏迅速、不能充分发挥其抽采效能等问题,通过对比分析留巷钻孔开孔位置分别选在留巷采空区侧、顶板中间和实体煤侧钻场时钻孔特点和护孔措施,确定了实体煤侧钻场为留巷钻孔的最佳布孔位置。据此,采用FLAC^3D模拟软件对工作面开采过程中充填墙体、巷道围岩和钻孔套管应力场变化规律进行了研究,结合相似模拟得出的破断线与卸压线位置,揭示了从孔口至终孔留巷钻孔的破坏形式可分为压剪破坏、压剪-剪拉过渡和剪拉破坏形式。基于此,提出了扩孔让压的护孔措施并进行了3种不同让压类型钻孔的现场抽采试验。结果表明:大直径单层套管让压型护孔方式实现了单孔瓦斯抽采纯量最大值4.90 m3/min,平均抽采体积分数84%,工作面过钻孔125 m时单孔瓦斯抽采量最大值达111 427 m3;且该类型钻孔施工方便、成本低,具有一定的推广应用价值。更多还原

【Abstract】 Aiming to problems of rapid destruction and low extraction efficiency of boreholes in the retaining roadway being affected by mining, a comparative analysis is carried out to study the properties and protection measures of boreholes. On the condition that opening locations of boreholes are chosen in the gob side, the over roof middle position or coal pillar of the retaining roadway. Consequently, the drilling field in coal pillar is optimally determined. Accordingly, the evolution rule of stress field in the filling wall, the surrounding rock and casing of boreholes is simulated by the FLAC^3D software in the mining process. Combing with the position of pressure relief line and rock broken line obtained by using similar material simulation experiments, the protection casing showed three failure types from orifice to the bottom in the axial direction, including the compression-shear failure, transition from compression-shear to shear-tension failure and shear-tension failure. Therefore, a novel drilling method is proposed, which can make the stress release properly through setting a certain gap. The field extraction test of three types stress-relief boreholes indicated that the maximum of methane extraction amount of large diameter boreholes with the protection of single layer casing protection are 4.90 m3/min. The average extraction concentration reached 84%. When the working face passes the borehole 125 m, the gas extraction of a single hole is 111 427 m3. Furthermore, this borehole is with the characteristics of convenient construction and lower cost, which can be remarkably applied values in similar mines.更多还原