Pressure relief law and application of deep-buried high-stress bedding coal by hydraulic flushing
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摘要: 为解决煤矿深部开采工作面煤与瓦斯突出危险性高的问题，以首山一矿12090工作面为工程背景，采用数值模拟方法分析了深埋藏高应力环境下采煤工作面顺层水力冲孔后的煤体变形和应力变化规律，得出结论：水力冲孔孔洞周围煤体朝向孔洞变形，有利于煤体内的裂隙发育和导通，进而提高煤体渗透率；冲孔区域煤体的水平应力有效降低，各冲孔孔洞形成的卸压区域相互连通，形成卸压条带，有利于瓦斯运移与抽采。依据数值模拟结果并结合实际工程，确定了首山一矿12090工作面水力冲孔工程方案：上帮钻孔角度为5~6°，下帮钻孔角度为−5~−4°；钻孔间距为4 m，每个冲孔孔洞长度为1 m，每个钻孔的冲孔孔洞间距为7 m，距巷帮30 m范围内不进行冲孔作业；冲孔水压为5~6 MPa，流量为120~160 L/min。实践表明：采用该方案后，每月成孔数达40个，成孔率达80%；冲孔钻孔瓦斯抽采浓度高、衰减慢，抽采50 d后冲孔钻孔内瓦斯体积分数为40%~60%，为普通钻孔的2~3倍，抽采120 d后冲孔钻孔内瓦斯体积分数仍有20%，水力冲孔有效提高了瓦斯抽采效果，降低了煤层瓦斯含量；回风流平均瓦斯体积分数降至0.5%以下；工作面平均日进尺由2.4 m增加至3.2 m，提高了生产率。Abstract: In order to solve the problem of the high risk of coal and gas outburst in deep coal working face, taking 12090 working face of Shoushan No.1 Coal Mine as the engineering background, the paper analyzes the deformation and stress variation law of coal body after hydraulic flushing in coal working face under deep-buried and high-stress environment by numerical simulation method. The conclusions are listed as follows. The coal body around the hydraulic flushing hole deforms towards the hole, which is conducive to the development and conduction of cracks in the coal body, thus improving the permeability of the coal body. The horizontal stress of the coal body in the flushing area is effectively reduced. The pressure relief areas formed by each punching hole are interconnected to form a pressure relief strip, which is conducive to gas migration and extraction. According to the numerical simulation results and the actual project, the hydraulic flushing project scheme of 12090 working face in Shoushan No. 1 Coal Mine is determined. The upper side drilling angle is 5-6°, and the lower side drilling angle is −5-−4°. The drilling spacing is 4 m, and the length of each punching hole is 1 m. The spacing of flushing holes in each borehole is 7 m, and no flushing operation is carried out within 30 m from the roadway side. The flushing water pressure is 5-6 MPa, and the flow rate is 120-160 L/min. The practice shows that after adopting this scheme, the number of holes completed per month reaches 40 and the completion rate reaches 80%. The gas extraction concentration in the flushing hole is high and the gas attenuation is slow. After 50 days of extraction, the gas volume fraction in the flushing hole is 40%-60%, which is 2-3 times of that in the ordinary hole. After 120 days of extraction, the gas volume fraction in the flushing hole is still 20%. Hydraulic flushing effectively improves the gas extraction effect and reduces the gas content in coal seams. The average gas volume fraction of return air flow decreases to below 0.5%. The average daily footage of the working face increases from 2.4 m to 3.2 m, which improves productivity.
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图 3 12090工作面顺层水力冲孔数值模型
Figure 3. Numerical model of bedding hydraulic flushing in 12090 working face
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图 7 钻孔间距为4，8 m时煤体变形对比
Figure 7. Coal deformation comparison under the borehole spacing of 4 m and 8 m separately
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图 8 钻孔间距为8 m时煤体X方向应力分布
Figure 8. Coal stress distribution at X direction under the borehole spacing of 8 m
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图 9 不同直径钻杆对应的上帮孔深
Figure 9. Borehole depth of upper side under different drill pipe diameters
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图 12 冲孔后风流瓦斯浓度变化
Figure 12. Change of gas concentration in air flow after hydraulic flushing
表 1 数值模型物理力学参数
Table 1 Mechanical mechanics parameters of numerical model
岩层 体积模
量/GPa剪切模
量/GPa黏聚力/
MPa抗拉强
度/MPa内摩擦
角/（°）密度/
（kg·m−3）顶板/
底板12 9 5 3 33 2500 煤层 3.26 1.28 0.57 0.33 48 1438 
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