Study On The Pressure-relief Gas Extraction Technique Under The Conditions Of Protective Layer Mining

Researching and analyzing the distribution regularity of stress field,the fracture characteristics and the technology of gas extraction with pressure relief after the protective layer on the mining and the gas extraction technology of the protective layer of C15coal in system by taking the upper protective layer C15coal mining of Xieyi in Huainan mining group as a engineering example.The research has a great significance to realize the safe and efficient production of coal and gas outburst mines,the sustainable development of coal mine and promote the promotion and application of the technology with upper protective layer on the mining.It is the principle of eliminating the hazard of coal and gas outburst of the protected coal seam by mining protective layer:the strata of the face roof and floor has different degree of movement and deformation,the stress state redistribution and the permeability coefficient changing obvious under the influence of the coal mining.Researching in system with the pressure relief features,the deformation,the fracture characteristics and the gas extraction method of the pressure relief of the underlying coal and strata after the upper protective layer mining by comprehensive analyzing the research technique of a large number of theory analysis,the numeric simulation test with computer,the field practice and so forth.The biggest expansion deformation is33.4mm and the expansion deformation rate was8.4%o of the protection layer of C13coal seam and more than6.0‰that is the threshold to judge the protected outburst danger;permeability coefficient is increased by401times that is from the original0.0718m2/(MPa2.d) change to28.8063m2/(MPa2.d);it has a good effect on the pressure relief and increase permeability that the pressure of the coal seam reduce by the initial4.9MPa to0.48MPa and the extraction rate of68%.Comprehensively researching and analyzing of the parameters by protective layer C15coal seam mining working face tail gas drainage,working face return air lane and tail wind exhaust gas comprehensive gas control in practice and the pressure relief gas drainage with mesh up wearing layer drilling of the floor roadway in C13protected layer,the results show that releasing the gas potential energy,reducing the gas content and eliminating the protected coal seam outburst danger by the application of protective layer of C15coal mining and the technology of pressure relief gas drainage,it makes C13coal seam with coal and gas outburst danger turn into the coal seam with low gas and no outburst danger in successful.Realizing the safe and efficient mining of protection layer C13coal in the end.