Study On Permeability Evolution Law Of Overlying Strata Under Ultra-Thick Seam Mining In Laosangou Coal Mine

Permeability evolution law of overlying strata under the influence of mining are studied based on the Laosangou coal mine's geological conditions.According to typical rock samples' permeability test under different stress path,the relation between permeability and volumetric strain are obtained.Then this relation is applied to the numerical simulation model of Laosangou coal mine's permeability evolution law of overlying strata under different mining parameter.Main achievements are as follows:The results of permeability test under complete stress strain path of typical rock samples from aquifuge and aquifer show that: the permeability change trend of two type rock samples are similar under continuously increasing of axial displacement.Under this progress permeability of rock samples from aquifer are 100 times larger than permeability of rock samples from aquifuge.The results of permeability test under mining stress path show that: under the influence of mining stress permeability of rock samples are continuously increasing and confining pressure have big influence of rock samples' permeability.The results of permeability test under residual strength stage of typical rock samples from different buried depth show that: confining pressure have big influence of rock samples' permeability under residual strength stage,rock sample's permeability increase with the decreasing of confining pressure.Gaussian function are used to fit the equation between permeability and volumetric strain of Lansangou coal mine's typical rock samples.Based on this equation,numerical simulation model of permeability test under complete stress strain path is established.Numerical simulation results indicate that the way of numerical simulation model's establishment is reasonable and fitting parameters are reliable.Laosangou coal mine's permeability evolution law of overlying strata under different mining parameter are studied.According to study results:(1)With the increase of mining thickness,the area of permeability increase continuously extend and the maximum permeability continuously increase.The area of permeability increase under 10 m mining thickness is 2.78 times as large as the area of permeability increase under 5m mining thickness.The area of permeability increase under 20 m mining thickness is 8.98 times as large as the area of permeability increase under 5m mining thickness.The maximum permeability under 10 m mining thickness is 1.29 times as large as the maximum permeability under 5m mining thickness.The maximum permeability under 20 m mining thickness is 3.81 times as large as the maximum permeability under 5m mining thickness.(2)With the increase of distance from the coal seam,the influence of mining to the strata's permeability and volumetric strain is decrease.