工作面采动煤体卸压增透效应研究与应用

Application and Study on Permeability Improvement Effect by Pressure Relief in Mining-induced Coal Body

为研究采煤工作面前方煤体卸压增透效应,提高煤体卸压瓦斯抽采量,分析了采煤工作面前方采动煤体变形破坏与渗透率变化过程的相关性,在工作面前方卸压区,煤体发生滑移破坏,有明显的扩容及卸压增透效应。现场实测了工作面前方煤体应力及钻孔瓦斯流量随工作面推进过程的变化规律,确定了支承压力区、卸压区分布范围。在卸压区内,因煤体渗透率增大,钻孔瓦斯平均流量提高2~3倍。基于工作面前方煤体卸压增透效应,根据不同钻孔失效距离及卸压区宽度,给出了不同偏角(钻孔与垂直煤壁方向夹角)下的预抽钻孔卸压瓦斯抽采量计算式。分析结果表明:钻孔偏角越大,卸压瓦斯抽采量越大。结合某矿N2105工作面现场条件进行计算,得出钻孔偏角最大可为21.4°,相比原垂直煤壁钻孔,单孔卸压瓦斯抽采量可增加978.5 m3,预期可有效提高本煤层瓦斯抽采率。

In order to study the coal body permeability improvement effect by pressure relief ahead of mining face and improve gas drainage quantity,the paper analyzed the correlation of coal body deformation failure and permeability change ahead of mining face.In pressure relief zone ahead of mining face,coal body slip failure occurred,which had marked expansion and permeability improvement effect.The authors tested the change laws of coal body stress ahead of working face and boreholes gas flow with advance of the face in site,the distribution scope of the abutment pressure zone and pressure relief zone were determined.In pressure relief zone,because coal permeability increased, the average borehole gas flow increased by 2~3 times.Based on coal permeability increasing effect by pressure relief ahead of coal face,pre-drainage boreholes pressure relief gas drainage quantity calculation formula with different angles were achieved on the basis of varied borehole failure distance and pressure relief zone width.The results showed that the larger the borehole angle was,the bigger pressure relief gas drainage quantity was.In combination with geological conditions of No.N2015 coal face in some mine to calculate,borehole angle could reach the max value 21.4°,compared with original coal body vertical boreholes,single pressure relief borehole gas drainage could improve 978.5 m3 ,which could effectively improve the coal seam gas drainage rate.