Study On Mining Fracture Distribution After The Lower Protective Seam Was Mined And Pressure-relief Gas Drainage

By the theory of lower protective seam mining and pressure-relief gas theory, this paper analyzes the structural evolution regularity of the overlying coal and rock after the lower protective seam was mined and the fow regularity of the pressure-relief gas in the protected coal seams affected by mining. To the destruction and displacement regularity of the overlying coal and rock,besides,the fracture distribution characteristics and change characteristics of stress after the lower protective seam was mined, by use numerical simulation software, this paper carried out a research and analysis. According to the theoretical analysis,the numerical results and construction site-specific circumstances, for pressure relief gas drainage system, it was optimized and designed.The field test achieved good results.Field test shows:after adopted the three-dimensional drainage system of ground drilling combined with drilling from1231(3) bottom road beat up a dense network type to wear13-1coal to extract pressure-relief gas, the total extraction rate reached86.6%,ground drilling extraction rate reached36.2%too; Coal seam gas content and pressure within the scope of protection decreased to highlight the critical value; Seam permeability coefficient is236times the original;the protective layer have been fully Relief,eliminate a prominent risk;Ground drilling can be a long, effective drainage on pressure relief gas within13-1seams.The results obtained from overlying coal and rock damage,deformation after the lower protective strata was mined,mined fracture distribution regularity comprehensive study and pressure-relief gas drainage,this paper can provide a reference for the mine has outstanding dangerous at pressure-relief gas extraction after the lower protective seam was mined.