Influence of primary key stratum structure stability on evolution of water flowing fracture

Abstract：According to unusual development of water flowing fracture in some coal mines,further research on influence of primary key stratum stability to evolution of roof water flowing fracture and water level was carried out using methods of simulation experiment and engineering detection.The result indicates that water flowing fracture could reach the top of bedrock when the distance from primary key stratum to coal seam is less than 7~10 times of mining thickness,while the water flowing fracture above the primary key stratum,there appears two evolution types.When stable movement happens,in the process of stability from breakage,rotation to counter rotation of primary key stratum,the water flowing fracture experienced ＇emergence-development-closure＇.While sliding instability occurs,the water flowing fracture is hard to close with mining.The engineering detection results proved the law of primary key stratum structure stability on evolution of water flowing fracture.Therefore,measurement such as increasing support resistance can be used to avoid the sliding instability of main key stratum,which makes the water flowing fracture close progressively with mining and the water level gradually recovered to realize the aim of coal mining under water-containing.