Evaluation Of Conditions Under The Lower Coal Seam During Mining With Pressure In Zhaozhuang Mine

In China,the coal resources are very rich which accounting for 68% of China's total energy consumption.Along with the shallow coal resources dried up,the depth of the mine extend continuously,in the process of the lower coal seam mining and the threat of the Ordovician limestone water is increasing.Therefore,how to solve the problem of lower coal seam mining under the pressure has an important guiding significance for mine safety production.As the Zhaozhuang Mine upper coal seam is not enough to need to maintain normal production,so it is urgent to mining the 15# coal seam,and the 15# coal seam is closer to the bottom of the Ordovician aquifer,the aquitard is less than 20 meters in some areas andthe water pressure is larger.Therefore,in this paper,throughcollection the aquicludethickness of 15 # coal floor and water separation performance;Based on the results of FLAC-3D simulation and empirical formula,determined floor failure depth and confined water lift height;analysis the 15# coal floor effective thickness and its spatial distribution characteristics.Finally,calculated the Ordovician limestone water inrush coefficient of 15# coal seam and carried out the safety zoning.The main research results are as follows:(1)Based on the Ordovician limestone lithology and borehole data,the the top of Ordovician Group has 30 m relative aquiclude;the 15# coal floor aquifuge thickness is between 38.75~67.25 m,the average thickness is 57 m,and the water resistance of aquifuge is good.(2)The results of FLAC-3D numerical simulation and empirical formula calculation show that the failure depth of 15 coal seam floor is 28 m,athe height of the pressure of the bottom plate is 7m.The effective aquiclude thickness of 15# coal seam floor is between 3.75 m and 32.25 m.(3)The water inrush coefficient of 15# coal floor is between 0.003MPa/m and 0.1MPa/m.therefore,the whole field is divided into two areas,safe area(the water inrush coefficient less than 0.06MPa/m)and risk area(the water inrush coefficient between 0.06 ~ 0.1MPa/m).