Underlying Coal and Rock Mechanics Features and Gas Drainage Effect of Upper Protective Seam Mining

Based on the rock fracture failure theory and the finite element calculation method, the protective seam mining process, underlying coal and rock stress and deformation features were simulated.With the protective seam mining variation law and the protected seam deformation, the underlying coal and rock stress would have a variation law from a compression, swelling, swelling reduced to stable.An industrial test was conducted at the mine site.The site investigation was made on the p rotective seam mining process, the protected seam deformation and the seam permeability variation. The theoretical analysis and the site measurement were basically t he same .According to the study conclusion, the design on the pressure releasing and gas drainage of the protected seam was optimized.With the pressure releasing an d gas drainage of the protected seam, the residual gas content was reduced to 2.33 m3/t, the residual gas pressure was reduced to 0.35 MPa and the residual gas cont ent and the residual gas pressure were all lower than the seam outburst critical value.The seam gas drainage rate within the protected scope was reached to 44.8%.Th e gas content of the protected seam was effectively reduced, the outburst danger was eliminated and the safety mining of the protected seam could be ensured.