Study On The Mining Technology Of Protective Coal Seam And Gas Drainage In Pressure Releasing Area With Closed Distance

For the coal and gas outburst coal seam,caving protective coal seam is one of the most effective methods.The existed problems on the protection scope demarcation of upper protective seam and on the drainage of the pressure relief gas in exploiting inclined seam group in Tunlan coal Mine were reviewed.Protection scope demarcating methods on upper protective layer mining in exploiting inclined seam were studied by theory analysis,numerical simulation and field investigation.Application of the pressure relief theory of the upper protective layers mining,analyze the pressure relief rule of the protectived layer and calculate the damage depth in the floor.Analyze the emission rule of the pressure relief gas in the protectived layer according to the floating and accumulating phenomenon and migration rule of the gas.The change processes of stress field,deformation field and plastic zone of the protected seam and the change rule of influence effect to the 2#coal seam were simulated by FLAC3D software after the inclined upper-protective layer of the first Mine of Tunlan was mined.Through the research to determine the pressure relief front of the protected layer than the upper protective layer lag about 37m,and according to the deformation criterion of the coal seam defining the protection scope after the upper protective layer mined,the stress-relief angle of the upper-protective layer along trend is 59°,and the inclinated angle is 74°.According to the field investigation about the effect on pressure relief of the upper protective layer,the residual gas pressure and the residual gas content is down to 0.55MPa and 5.21411/t of the protected layer are below the critical value.The gas drainage rate can reach 42.5%in the 02#coal seam protection range,eliminate outburst danger,and the safety of working face can be guaranteed with the measures of reasonable layout of drilling,designing the gas drainage method,using bed plate tunnel and upward holes with network format to drain.