| With the exploitation of coal seam above confined aquifer, the floor rock crack under the effect of fluid-solid development, expansion, eventually induce floor water inrush, and serious threat to the mine safety production. For a long time, domestic scholars have carried out a lot of research work on the mining failure characteristics and the water-inrush from the level and nearly horizontal coal seam floor, and have achieved fruitful theoretical results. Although the above theoretical methods are useful for the prediction and prevention of mine water disasters,the studies on the deformation and failure characteristics and seepage characteristics of inclined coal seam floor are are still some insufficiencies. Therefore, this paper used the methods of theoretical analysis, numerical simulation combined with field measurement to study the floor mining failure characteristics and the risk of mine floor water inrush for an inclined coal seam, and achieved some innovative results as follows:(1)Considering the impact of the confined water pressure and the dip Angle of coal seam on an mining floor, based on the spatial semi-infinite body theory and the Mohr-Cou- lomb failure criteria, combined with the characteristics of the abutment pressure distribution of inclined coal seam with longwall mining along the strike, the inclined coal seam floor mining stress and failure depth solving mechanics model are established, respectively, and the horizontal stress, the shear stress and the maximum failure depth in any position of a coal seam mining floor are calculated.(2) According to the design scheme of the orthogonal test, the working floor failure depth are simulated and tested via FLAC~3D, and matrix analysis and variance analysis are adopted to perform simulation results, respectively, with the sensitivity of each main control factor of the floor failure depth determined. Simultaneously, the optimal scheme for an orthogonal simulation test is obtained, which can effectively reduce the danger of floor water inrush with the minimum floor failure depth.(3) According to the thin plate theory, a deflection solving mechanical model of the water-resisting key layer of an inclined coal seam floor is established, and the deflection value of the key layer of an inclined coal seam floor is calculated, combined with the Mohr-Coulomb failure criterion in the elastic mechanics, and the mechanical criterion expression of water-inrush in any position of the water-resisting key layer.(4) Logistic regression analysis of the principal component and logistic regression analysis are performed on the main control factors of floor water inrush. The results of regression analysis show that the average accuracy rate of logistic regression analysis of the principal component is around 10% higher than that of logistic regression analysis. The average accuracy rate of the floor water inrush regression model established by logistic regression analysis of the principal component is higher, combined with the actual mining geological parameters, and it, to a certain extent, can make qualitative prediction on inclined coal seam floor water inrush.(5) Based on the numerical simulation software of FLAC~3D, the fluid-solid coupling numerical calculation model of an inclined coal seam above a confined aquifer is established.With the advance of the working face, the dynamic evolution process of pore water pressure and seepage vector in an inclined coal seam floor is simulated and analyzed, and the floor water inrush high risk area is determined, which provides a theoretical basis for the prediction and prevention of water inrush from an inclined coal seam.(6) The three-dimensional deflection surface of the deflection function of a water-res-isting key layer and the isoline nephogram of the floor deflection function of (x, y) were draw, and the mechanical criterion expression f(x0,y0) of the first water inrush position of the 3303 working face floor water-resisting key layer with the maximum limit water pressure of the layer given. |
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