The Research Of Gas Pressure Relief On Extraction Of Protective Seam In Yangdong Coal Mine

Coal and gas outburst have occurred in gassy mine in recent years,as exploit increase of depth with mine,the geologic conditions are complex,such as Handan,Huainan,Pingdingshan,Shanxi,Guizhou,Yunnan,and like,The frequencies of gas outburst increase,the number of coal seam with outburst hazard gradual increase which is a serious threat to the coal mine production safety.First of all,these mining areas are mining of seam group,which the main minable coal are almost all high gas outburst seat with low permeability.So protection layer mining was widely used as a sort of cost-effective regional measures for outburst prevention.Taking “improvement of mine environment and utilization of gas resource ”as a point,protection layer mining would cause full pressure of adjacent coal seam and greatly improves gas permeability of coal seam.Second,accomplishing gas drainage sufficiently of pressure relief gas is another main objective of protection layer mining,based on rationally optimizing layout of the gas drainage drills.And can also achieve reasonable layout of recovery working face of protected coal seams and driving and mining efficiently.French became the first country to use of protection layer mining since 1933,and now it gained widespread adoption in almost all country which with coal and methane outburst mines,such as china,Russia,Poland,Bulgaria,Germany,Holland,Belgium.In the end,protective layer refers to first mining non-outburst coal seam within mine or seam group which has certain outburst dangerous,protecting adjacent seam.After mining protection layer,the roof and floor of protective layer(including outburst coal seam being protected)would severe swelling deformation.The original stress of protected coal seam would reduce;the coal mass would be deformation with coal seam permeability and the cracks increase.This would make coal seam permeability significantly increased,providing good condition for gas flow.In the effect of gas pressure in coal seam,the gas within protected coal seam constant flows by the cracks and fissures in the rock of the roof and floor of outburst coal seam to mining space of protected layer,or gas drainage drills of protected layer effectively.Through this,the gas pressure of within protected coal seam reduces unceasingly,adsorption gas can be desorbed rapidly to free gas becoming uninterrupted content of gas supplying gas flow.The content of gas about protected coal seam reduced unceasingly,while strength and stability of coal seal have increased.Series of changes above-mentioned will make the protected coal seam gradually losing essential requirements to gas outburst,avoiding the occur of outburst.Be limitProtection layer mining are more effective than local prevent to coal and gas outburst prevention and control,and the safety and reliability are also better.To test site,the change of gs permeability of coal seam have not been investigated after protection layer mining.It is suggested for Yangdong coal mine to comparative analysis when there is a suitable location in later years.