顶板定向瓦斯抽采钻孔合理层位确定及其抽采效果分析

Research on reasonable horizon determination and drainage effect analysis of roof directional gas drainage boreholes

深部厚煤层工作面快速回采常诱发瓦斯异常涌出。根据唐口煤矿6305工作面工程条件,采用经验公式计算了6305工作面顶板导气裂缝带的高度区间,通过Fluent模拟分析了定向长钻孔的最佳设计层位,施工了3组4个定向长钻孔,观测定向钻孔抽采瓦斯情况,并与传统的高位钻孔进行技术经济比较。结果表明:6305工作面顶板裂缝带的区间高度距离煤层底板17.4~45.5 m,定向长钻孔的最佳布置层位为距离煤层底板4倍采高(40.32 m)处;顶板定向长钻孔瓦斯抽采量为39~44 m^(3)/min,瓦斯抽采浓度可达15%,瓦斯抽采纯量为3~5 m^(3)/min;与高位钻场钻孔抽采相比,采用顶板定向钻孔抽采裂缝带瓦斯能够在保证不降低瓦斯治理效果的前提下,总钻孔工程量减少50%,施工时间缩短72%,每500 m回采巷道节约成本100万元。

Rapid recovery of working face in deep and thick coal seams often induces abnormal gas emission.According to the engineering conditions of 6305 working face in Tangkou Coal Mine,the height interval of the air conduction fracture zone in the roof of 6305 working face was calculated by theoretical formula,the optimal design horizon of directional long borehole was analyzed by Fluent simulation and 4 long directional boreholes in 3 groups were constructed.The gas drainage effect by directional boreholes was observed and compared with the traditional high-level boreholes.The results showed that the interval height of the roof fracture zone of 6305 working face was 14-45 m from the coal seam floor;the distance of optimal layout horizon of the directional long borehole from the coal seam floor was 40.32 m which was equal to 4 times of mining height;the gas drainage volume of the roof directional long borehole was 39-44 m^(3)/min,and the gas concentration reached 15%,and the pure gas volume was 3-5 m^(3)/min;compared with the traditional high-level borehole gas drainage,the roof directional borehole gas drainage could reduce the total borehole engineering amount by 50% and the construction time by 72%,and save 1 million yuan in cost per 500 m mining roadway without reducing the gas control effect.