近距离煤层采空区下综放工作面巷道合理位置研究

Research on the optimal position of roadways in fully mechanized caving faces in mine-out areas of close distance coal seams

近距离煤层综放工作面开采空间大,采动强度高,下位煤层回采巷道受上煤层采动影响存在应力集中、巷道支护困难等问题,因此近距离煤层综放工作面巷道合理位置的选取对后期支护控制起到关键性作用。以西露天煤矿2煤层和1煤层1分层为研究对象,综合考虑了上煤层开采时的底板应力降低区域和下煤层开采时的极限平衡区域,确定了下煤层巷道的合理位置应在距离实体煤柱内错22.79 m以上的区域。基于上述理论计算结果,分析了上煤层开采后底板应力分布规律及不同内错距下巷道围岩变形破坏特征及规律,结果表明:①距离采空区底板越近,应力最大值与最小值相差越明显;②随着内错距不断增大,围岩应力和应力集中系数呈现急剧降低-缓慢增大-稳定的趋势,在内错距20~25 m内应力及应力集中系数相对较小;③巷道围岩塑性区范围呈现先减小后增大的趋势,当巷道处于内错20,25 m时巷道围岩破坏相对较小;④巷道变形量随着内错距增大而逐渐减小,当内错距增加至25 m时,巷道围岩移进量基本保持不变;⑤确定巷道合理内错距为20~25 m。工程应用结果表明:巷道采用内错距24 m布置时,巷道围岩松动破坏深度及变形量均在可控范围内,进一步证明了该内错距的合理性。

Fully mechanized caving faces in close-distance coal seams involve extensive extraction spaces and high mining intensity.The extraction of roadways in lower coal seams is affected by stress concentration and support challenges resulting from the mining of upper seams.Hence,determining the optimal roadway position is crucial for effective support control in these settings.This study focused on the No.2 coal seam and the No.1-1 sub-seam at Xilutian Coal Mine.It evaluated both the stress reduction zone in the floor caused by upper seam extraction and the limit equilibrium zone during lower seam extraction,concluding that the optimal roadway position should be more than 22.79 meters away from the solid coal pillar.Theoretical calculations were used to analyze the stress distribution pattern in the floor following upper seam extraction,as well as the deformation and failure characteristics of the surrounding rock at various internal offsets.The results revealed:①A pronounced difference between maximum and minimum stresses occurred closer to the floor of the mine-out area.②With increasing internal offset,the surrounding rock stress and stress concentration coefficient initially decreased sharply,then increased slowly,and eventually stabilized,with relatively low values observed within the 20-25 meters internal offset range.③The plastic zone of the surrounding rock decreased and then increased,with minimal damage to the roadway rock observed at internal offsets of 20 and 25 meters.④Roadway deformation decreased as the internal offset increased,and surrounding rock displacement stabilized when the internal offset reached 25 meters.⑤The optimal internal offset for the roadway was determined to be 20-25 meters.Engineering applications confirmed that a 24-meter internal offset maintained both rock looseness and deformation within controllable limits,further validating this internal offset.