近距离薄煤层群上保护层开采邻近层卸压瓦斯抽采模式探究*

为研究近距离薄煤层群上保护层开采期间邻近层卸压瓦斯对回采工作面瓦斯涌出的影响，进而有效杜绝保护层开采过程中工作面瓦斯积聚或超限等事故，结合煤岩体破碎前“应力-裂隙-渗透率”间关系，建立卸压瓦斯三维渗流模型。采用Flac3D软件，以新维煤矿煤层条件为工程背景，研究保护层开采过程采场渗透率沿纵向分布规律，确立下保护层C3煤层处于三维增渗区、C7与C8号煤层处于水平增渗区。基于此，提出“近场定向钻孔全覆盖抽采与远场穿层钻孔层间卸压抽采结合”的瓦斯治理技术模式，并开展现场试验，结果表明:试验工作面回风瓦斯浓度降低44.4%，绝对瓦斯涌出量降低52.3%，该模式可显著提高卸压瓦斯的治理效果，为类似工况下的保护层开采提出1种新的瓦斯抽采模式，具有一定的指导及借鉴意义。

Research on pressure-relief gas drainage mode of adjacent coal seams in upper protective layer mining of close thin coal seam group

To study the influence of pressure-relief gas from adjacent coal seams on the gas emission from working face during the upper protective layer mining of close thin coal seam groups,and also effectively prevent the gas accumulation or overrun accidents in the working face during the process of protective layer mining,combining the relationship among stress,fracture and permeability before the breaking of coal and rock mass,a three-dimensional seepage model of pressure-relief gas was established.Taking the coal seam conditions of Xinwei coal mine as the engineering background,the Flac3D software was used to study the longitudinal distribution laws of stope permeability during the process of protective layer mining,and it was determined that the lower protective layer C3 coal seam was in the three-dimensional increased permeability area,and the C7 and C8 coal seams were in the horizontal increased permeability area.On this basis,a gas control technology mode of “combination of full-coverage drainage by near-field directional boreholes and interlayer pressure-relief drainage by far-field cross-layer boreholes” was proposed,and the on-site tests were carried out.The results showed that the return air gas concentration of tested working face was reduced by 44.4%,and the absolute gas emission amount was reduced by 52.3%.This mode could significantly improve the control effect of pressure-relief gas,and proposed a new gas drainage mode for the protective layer mining under similar working conditions,which has certain guidance and reference significance.