Study Of Overburden Water Flowing Fractured Zone Height Of Steep Seam Mining

China is one of the countries which have the world's most abundant coal resources. With the strength of the coal mining increased,steep seam mining are attracting increasing attention. The study of surrounding rock deformation and water flowing fractured zoneheight of the steep seam mining is a major issue of the Western coal mining. Especially for the steep seams which are under the rivers,karst water,old kiln water and impacted by the surface water infiltration in the rainy season. Mine water hazard prevention and control is a serious problem that can not be ignored on mine safety production. This paper studies YunNan guishan steep seam,on the basis of participation tutor's subject of research on complex coal mining, using a new method study the overburden failure law and water flowing fractured zone height of the steep seam mining under pore water pressure that caused by rainfall.First, using F-RFPA^2D numerical simulation of sandstone aquifer of the coal seam roof, detailly analyzed the whole failure process of rocks under pore pressure and no pore pressure. Obtained the whole process of stress-strain and permeability curves of the of rock. Simulated the rock damage under the same confining pressure and different pore pressure, got the curve between the rock damage strength and the porosity pressure curve. Through the curve fitting obtained the curve equation;Secondly, using material mechanics elastic mechanics and fracture mechanics, analyzed the physical chemistry effection and mechanical principle effection of pore pressure. Discussed the effection of pore pressure on the mechanical properties of sandstone, emphatically analyzed pore pressure's effection on rock failure mode. Reveals the mechanism of the overburden rock water flowing fractured zone height changes caused by water pore pressure.Finally, using the results of these studies, combination of steep seam overburden failure theory, puts forward the influential action of the pore pressure to the cover rocks movement features and the failure structureof steep seam ,and the mining working face 31139 were analyzed with a numerical simulation soft of FLAC^3D.Research suggests roof rock strength and deformation modulus has been changed as impact of pore-water pressure. These changes caused different failure law of overburden and hydraulic conductivity fracture zone height compared with no pore pressure. Using the water flowing fractured zone height empirical formula of steep seam and field observation data proved the correctness of the simulation results without pore pressure. At the same time, proposed there is a certain difference between rempirical formula and the actual result that consided the pore pressure. Applicated the theory to simulated the rock damage conditions of different sub-cover hight and demonstrated the height of 70m sublevel under the geological conditions is beneficial to face safe production.And using the regression analysis theory analysed the simulation results, obtained the fitting equation of sublevel height and overburden water flowing fractured zone height under the 2MPa pore pressure.