Mechanism Of Water Inrush For Coal Mine Deep Exploitation

The water supply and water drain channel is a general conditions for water bursting inmine. For the water inrush in the karst floor, the characteristic of the karst aquifer is theimportant factor for the studies of the water supply. For the water drain channel, the structureof the water-resisting layer in karst floor must be investigated. The mechanism of the waterinrush in the karst floor is very important for the prevention of water inrush accident. Basedon Wangfeng mine Tianxia group and the coal bed exploitation under the high pressureaquifer, water inrush induced by the water-resisting layer exploitation in karst floor is studiedin this paper.Firstly, six influence factor is obtained by the analyses of water inrush data, e.g., thewatery of aquifer, water head pressure and lithology of the rock layer, geological structure,pressure of surrounding rock and exploitation method. The stress-strain and seep flowrelationships of rock is interrelated with the lithology and the confining pressure. Thepermeability of rock is varied with the crack and the porosity. Based on the hydrogeololgyand engineering geology characteristic of the aquifer of Wangfeng mine Tianxia group, twofundamental types of water inrush for Wangfeng mine Tianxia group is proposed, e.g., waterinrush in the perfect karst floor and water inrush in the perfect karst floor. Based on the threezone theory, the mechanism of the water inrush in the karst floor is studied with the boundwater and rock interaction. A criterion for water inrush determination is proposed in thispaper.Secondly, the characteristics of the deep karst aquifer is studied. The karst aquifer isinhomogeneous distributed in plane and vertical directions. The permeability and the wateryof deep karst is decreased with the depth increased. The Ordovician limestone is compoundedby several aquifer, the second segment of the upper Majiagou group have the most watery andclosed to the coal.Thirdly, the top of weathered Ordovician limestone is widely distributed in Huabeicoalfield. However, the rock pack of karst in weathering crust is agensis, and have goodcharacteristics of water resistance. The development and water-resisting property of the karstlocated in the upper Fengfeng group is investigated. The water-resisting layer in the upperFengfeng group is about40m.Finally, the exploitation of11th coal layer is analyzed by numerical simulation with different values of pore-pressure and thickness of water-resisting layer. The failuremechanism of water-resisting layer in deep karst floor is obtained in this paper. The crackingdepth and cracking range of rock in karst floor is irrelevance with the thickness ofwater-resisting layer, and the maximum depth of plastic area is about22.5m. Three methods isused for the stability of the karst floor for11th coal layer evaluation, and11th coal layer issafe for exploitation if the bottom without fault.The results of this paper is as a reference for coal exploitation in11th coal layer underhigh pressure aquifer, and also suitable for other coal mine exploitation.