Study on floor disaster-causing mechanism of fully-mechanized mining face crossing drainage roadway in water-rich area

To prevent delayed water inrush accidents during the fully-mechanized mining face crossing the intermediate roadway, this study takes the water inrush incident occurring in 1293 mining face of the east well in Gequan Coal Mine passing through the drainage roadway as the engineering background. By adopting methods including theoretical analysis, numerical simulation and field measurement, the disaster-causing mechanism of floor water inrush induced by the mining face crossing the drainage roadway was investigated. The results show that during the mining process, the floor rock stratum is divided into the original rock stress zone, compression zone, expansion zone and recompression zone, with the expansion zone posing the highest risk of water inrush. The initial position where Ordovician limestone water gushes into the coal seam floor is 15.8 m behind the mining face, where the floor failure depth reaches 12.1 m. Due to the existence of the drainage roadway, mining-induced stress overlaps with the surrounding rock stress of the roadway, leading to more severe damage to the surrounding rock near the drainage roadway than in other areas, and further resulting in stress unloading in this zone. After Ordovician limestone water flows into the floor fractures, it gushes out from the location of the drainage roadway (the stress unloading zone). The formation of water-conducting channels is a gradual process. During the mining of the lower coal group, it is necessary to actively detect the thickness of the aquifuge. When there is an intermediate roadway in front of the mining face, it should be filled in advance to avoid the adverse effects caused by the superposition of mining-induced stress and the surrounding rock stress of the roadway.