Research On The Permeation-Resisting Property Of Tectonic Disturbance Floor While Mining NO.21Coal With Pressure Above High Confined Water

With the increase of excavation depth, water-inrush accidents occur frequently during coalmining under pressure, which has seriously affected the safety in coal mine production. Statisticsshow that most of water-inrush from floor is influenced by tectonics, especially, in water-richaquifer of Ordovician limestone. Therefore, study on the mechanism, characteristics ofwater-inrush from floor induced by tectonic disturbance during coal mining above high confinedwater and the water resisting ability of the coal seam floor have great theoretical and practicalsignificance.Taking water-inrush actuality of Peigou Coal Mine in Zhengzhou Coal Group Company asthe object, this paper systematically analyzed the coal mining water inrush case from basicgeology. The result shows that several major water-inrush accidents once occurred are mainlylocated at fault segment, and fault structure is the weak link in the permeability of coal floor.Using elastic-plasticity theory, mechanical mechanism of normal fault activation and floordestruction caused by mining under water pressure was analyzed. The critical hydraulic pressureequation of floor was derived. In addition, the variation law of pressure bearing capacity offloor with fault dip, material composition, water pressure and the thickness of water-resistingfloor was also obtained. On this basis, the water-inrush process from different type faults underhigh water press has been simulated by model test. It is revealed that the seepage law shows poreflow converting to fractured flow and conduit flow in initial period. From porosity andpermeability, it presents pore expansion perforation stage developing into steady seepage stageand high resistance cracking stage developing into low resistance perforation stage.Considering the structure characteristics of floor rock mass, the intensity of permeability offloor aquifuge, effective aquifer thickness and so on, evaluation model of permeability conditionabout mining floor was established. We evaluated the permeability of floor in32071work faceof Peigou Mine. It is revealed that the floor of mining No.21seam is a good permeability barrierfor Ordovician limestone water in the normal structure state. Permeability ability of the floorunder the condition of fault disturbance is in limit state, where is the easy-happening location ofwater-inrush occurrence. Therefore, prevention measures of floor water-inrush were proposed.Finally, the grouting reconstruction effect was evaluated by the method of additional stressand water pressure observation. The testing results show that the grouting properly improves thestrength of fault rock, cuts off the hydraulic relations among different aquifers and improves theimpermeability of floor aquiclude. In brief, the grouting reconstruction effect is good.