Study On Water Inrush Mechanism Of Mining Fault

Mine water inrush is a difficult problem which is always puzzling mine production. Relying on 973 National Basic Research Program of China -Research on Basic Theory about the Mechanism of Water Inrush and its Prevention, centering on the science problem being to solved - the structure failure, fracture evolution and flow catastrophe laws of mining strata, the problems including mine water inrush precondition, the water inrush mechanism of fault activation and the water inrush prediction are discussed with theoretical analysis, numerical simulation and nonlinear method in this paper. The main research contents and results are as follows.The two preconditions of water inrush including water inrush source and pathway are summarized, and its hydrogeology features are analyzed with examples. The mechanical characteristics and hydrogeology features of fault are described with emphasis, which establish a foundation for the research of the paper.Based on the analysis of physical, chemical and mechanical actions of groundwater on rock, and the effect of groundwater on fault activation, water-rock interaction mechanism is studied. With the clamped beam theory of material mechanics, the open displacement equation of fault is built under water pressure. According to the D-M model of fracture mechanics, the crack initiation criterion of single fracture near fault is proposed under hydraulic and underground pressure. The effects of hydrolic pressure, lithologic characters and fault angle are also discussed.Through the research of failure mechanism of water-resisting floor, the concept of composed water-resisting floor is proposed. The nonlinear mechanical model of combined water-resisting floor is built, and its necessary and sufficient conditions of nonlinear destabilization are derived. The effects of soft rock's elastic modulus and tunnel span on the stability of the different composed water-resisting floor are analyzed. With rock mechanics theory, the effect of fault on the stability of water-resisting floor is discussed at the actions of mine pressure and hydraulic. The formula of critical water pressure supported by water-resisting strata is deduced, the water-inrush criterion is proposed simultaneously. Then the effect laws caused by the thickness of the water-resisting floor, the dip angle and cohesion force of fault on the water-resisting floor are analyzed.Based on the concept of water-resisting key strata, the water inrush mechanism of little fault activation under ground pressure and hydraulic is analyzed. The water inrush laws of little fault are simulated with RFPA-FLOW2D. The results show that there are three periods including little fault activation, activation area extending and fracture transfixion in the process of water inrush. With the understanding of the seepage flow field, it shows that the seepage flow field evolves with the fracture field simultaneously, and it can label the position of the coal face water inrush. The simulation results of water inrush induced by several faults show that the larger the distribution density of little faults is, the easier the water inrush will happen.For predicting the mine water inrush, the nonlinear prediction model of mine water inrush is established based on fractal and support vector machines theory. Under the Matlab environment, the calculating program is compiled with Libsvm. The mine water inrush of HeBi four mine in past years are predicted with the established model, and its prediction precision is discussed.For the engineering problem of mining under Lei River in Tong Jiao Wan mine, the mining method of combining the strip mining with the backfill one is proposed. And its reliability is verified with numerical simulation. Through comparing the filling effect of three different filling materials, the optimal one is determined.The water inrush mechanism of mining fault and mining water inrush prediction are researched in this dissertation based on the subject frontier, various theoretical and nonlinear methods. The results of this dissertation are useful both theoretically and practically, and established the foundation for the basic theory about the mechanism of water inrush.