Study On Water Release Law Of Low Permeability Roof Sandstone In Deep Mining And Engineering Application

With the deepening of coal mining depth,the sandstone fissure water in the roof of coal seam presents the characteristics of high pressure and low permeability.The characteristics of water inflow in the roof sandstone aquifer during the mining process of the working face are also different from those in the shallow part,especially in the working face mining length and inclined length equal parts of the water inflow suddenly increased.The water inflow has increased sharply,and the current method has been difficult to accurately predict the water inflow of the working face.Therefore,the thesis takes the 818 first mining face of Xinhu Coal Mine in Anhui Province as an example.On the basis of theoretical analysis,combined with numerical simulation and field test,the development mechanism of mining-induced fractures in low permeability sandstone of deep coal seam roof,the release law of static reserves and the prevention and control technology of water damage are studied and discussed in depth.According to the above research,the following research results have been achieved :(1)According to the empirical formula of multi-factor fitting,the development height of roof water-conducting fracture zone is predicted;The dynamic characteristics of deformation and failure of roof strata with coal seam mining are simulated by GDEM software,and the variation law of basic roof stress concentration at different advancing distances is analyzed;According to the measured value of water flowing fractured zone in working face,the predicted value of water flowing fractured zone is verified.(2)Based on the elastic thin plate theory,the distribution law of vertical fracture spacing in mining water-conducting fracture zone is revealed.By establishing the mechanical model under two boundary conditions,the critical expression of the breaking distance of the primary and periodic weighting of the overlying basic roof in the goaf is proposed.The mechanical mechanism of the working face ’s ’ square ’affecting the breaking distance of the basic roof is analyzed,and the vertical crack spacing distribution of the high conduction zone is obtained;Combined with the release characteristics of static reserves in roof aquifer,the release law of static reserves in roof low permeability aquifer is obtained,and the reason for the peak value of water inflow in working face is explained.(3)The mine audio frequency electric perspective technology is used to detect the water abundance in the range of 0 ～ 80 m of the roof.Combined with the structural characteristics of the roof,the position and spacing of the roof drainage holes are designed,and the effect of underground water discharge is evaluated.(4)Based on the water exploration and drainage project,the hydrogeological zoning of the working face is carried out.The hydrogeological parameters obtained by inversion are used to predict the change of water inflow in the working face by using the ’ dynamic and static combination ’ method.There is little difference between the predicted results and the actual measured results.The drainage system of 818 working face is designed to ensure the safe and efficient mining of the working face;The actual water inflow law of the working face is analyzed,and the optimization measures of the pre-mining drainage borehole layout of the low permeability roof are proposed.There are 58 figures,21 tables and 98 references in this thesis.