Study On Mechanism Of Fault Activation And Water-inrush Through Insidious Fault In Mining Floor

Mine water disaster is always a major issue affecting and restricting the coal mine safety in our country. Most of them could be related to fracture structure. Compared with the large fault, insidious faults spread more widely with more number, hide more deeply and not easy to detect, which more easily lead to mine water disaster. In this paper, for investigating mine water disaster caused by fault activation, different study methods including theoretical analysis, numerical simulation and field microseismic monitoring are applied to systematically explore the damage fracture evolution of aquifuge and mechanism of insidious fault activation and water inrush from mining floor, and to obtain the following innovational results:(1) Based on classical linear elastic fracture mechanics, model of insidious fault activation in mining floor is established. The analytic solution of effective shear stress along the fault plane is deduced. The influence of the mining depth, the burial depth of fault, the fault dip, the working face advancing direction, the abutment pressure concentration, the water pressure in aquifer and other factors on the activation of insidious fault in floor were analyzed. The stress intensity factor of fault front is used for establishing activation criterion of compressive shear faults, which reveals mechanical mechanism of insidious fault activation in mining floor.(2) Combining the particle flow software PFC and the continuous medium software FLAC, the PFC/FLAC coupling model of floor failure containing insidious fault is set up. It successfully simulates mesocrack initiation and growth of insidious fault in mining floor during workface advancing, revealing the influence of fault geometric and mechanical parameters, mining height and gob filling rate on insidious fault activation.(3) Considering the seepage stress coupling effect, PFC/FLAC numerical model of discrete-continuum coupling is set up for simulating fault activation and water-inrush through insidious fault in mining floor. The rise, expansion and inrush from floor of the confined water are investigated, revealing influence of fault geometric and mechanical parameters and water pressure on temporal and spatial evolution of water inrush channel of insidious fault, and providing a reference of mine water disaster prevention and control.(4) Using the high-precision microseismic monitoring technology, through continuous and dynamical monitoring, temporal and spatial distribution of microseismic events about failure of floor containing insidious fault are got. Combined with PFC/FLAC numerical model of discrete-continuum coupling and activation and water inrush criterion of insidious faults in floor, the law of insidious fault activation and water inrush risk is analysised deeply. Results of theoretical analysis, numerical simulation and microseismic monitoring are in good agreement. It proves validity of above theoretical model and numerical method for forecasting water inrush from insidious faults in mining floor, which has a good prospect of engineering application.