采空区顶板高位走向长钻孔高效抽采瓦斯机理研究

为了提高采空区顶板高位走向长钻孔瓦斯抽采效率,消除工作面上隅角瓦斯超限事故,以山西华晋吉宁煤业有限责任公司2102综采工作面为研究对象,采用数值模拟、理论分析与现场试验相结合的方法,利用3DEC软件模拟计算2102综采工作面回采期间采空区顶板裂隙场演化过程,根据裂隙场、应力场和应变场分布模拟结果在沿工作面推进方向上划分采空区顶板裂隙加强区范围与压实区范围,工作面推进期间煤层顶板在时间上先后经历裂隙加强区和重新压实区,处于裂隙加强区的钻孔部分为钻孔高效抽采作用区域,钻孔高效抽采段长度与钻孔高效抽采段裂隙发育程度共同决定高位走向长钻孔抽采效率,揭示了采空区顶板高位走向长钻孔高效抽采瓦斯作用机制;在此基础上,在采空区顶板裂隙带高度范围内布置多个高位试验钻孔,进行钻孔瓦斯抽采效果考察,研究结果表明:在保证高位钻孔布置于回风巷内侧顶板裂隙带前提下,最佳布孔层位为距煤层底板60 m左右,同时在高位试验钻孔作用下,上隅角瓦斯体积分数最大值由1.1%降低至0.6%,说明根据回风巷内侧采空区顶板裂隙带高度范围,布置高位走向长钻孔能显著降低上隅角瓦斯浓度。

Mechanism study on high efficiency gas drainage of high level strike long boreholes in gob roof

This paper is devoted to improve the gas extraction efficiency for high level strike long boreholes in gob roof and to eliminate the gas exceeding limit accidents of upper corner of mining face. A combining study of numerical simulation,theoretical analysis,and field test was conducted on No.2102 fully-mechanized mining face of Shanxi Huajin Jining Coal Industry Co.,Ltd. Firstly,the 3 DEC software was used to simulate the evolution process of crack field in gob roof of No.2102 fully-mechanized mining face during mining. According to the field distributions of fissure,stress,and strain from the simulation results,the roof of gob was divided into fissure strengthening area and compaction area along the mining face. During face advance,the roof of the coal seam passed the fracture strengthening area and the re-compaction area in sequence. The section of boreholes located in fracture strengthening area was the high efficiency extraction section.The mechanism of high efficiency gas drainage of high level strike long boreholes in gob was then revealed-the gas extraction efficiency of the high level boreholes was determined by the length and the development degree of the cracks of the high efficiency extraction section of the boreholes. Based on the mechanism,a number of high-level test boreholes were arranged in the roof fracture zone of the gob to investigate the gas drainage effect. The results show that the optimum location of the high level boreholes was about 60 m to ensure the high level boreholes in the inner roof fracture zone of return air roadways. When applying the high level test boreholes,the gas concentration in the upper corner was reduced from 1.1% to 0.6%. The results indicate that the gas concentration in upper corner could be significantly reduced by utilizing strike long boreholes within roof fissure zone in inner gob of return air roadways.