Study On Gas Treatment Technology Of Upper Protective Layer Working Face Of Close Coal Seam Group

China’s coal resources are mostly endowed with coal seam clusters and the coal mine gas hazard is more serious.Compared with single seam mining,the gas gushing situation is more complicated and difficult to manage under the close seam group mining conditions,and the protective seam mining technology is considered as one of the most cost-effective ways to manage the regional gas.Under the protective seam mining conditions,the unloading gas from the neighboring seam will gush into the protective seam working face,causing the working face to exceed the gas limit and easily inducing safety accidents in the mining site.Therefore,it is important to study the gas management technology of the working face of the protective seam on the close coal seam group for the safe and efficient production of coal mines.In this thesis,through theoretical analysis,numerical simulation,field test and other methods,under the mining conditions of protective seam on close coal seam group,a coal mine 2202working face is used as the research object,and the Y-type ventilation method along the air stay lane is adopted to study the damage characteristics of the rock layer at the bottom of the working face;the source of gas in the gob of the working face is determined,the gas distribution law of the gob under Y-type ventilation is revealed,and the gas enrichment in the gob is determined.On this basis,the air volume ratio control technology and buried pipe gas extraction technology under Y-type ventilation were proposed,and their technical parameters were optimized,and field industrial tests were conducted.The research results are as follows:(1)According to the production geological conditions and gas management needs of the test working face,the way of filling the lane next to the high water material lane was proposed,and the Y-type ventilation system was formed;according to the theoretical calculation and UDEC numerical simulation results,the damage depth of the bottom plate of the test working face and the damage law were studied,and the maximum damage depth of the bottom plate of the test working face was determined to be 10.76m,and the No.3 coal seam underneath it was in the damage zone of the bottom plate.The No.3 coal seam will be transported to the protection layer.(2)Through theoretical calculation and field measurement results,we studied the gas source and gushing characteristics in the gob of the test working face,and determined that the ratio of gas gushing from this coal seam and neighboring seams is about 5:5,and the absolute gas gushing volume in the gob is 26.38m~3/min;through FLUENT,we established the numerical calculation model of the gob,and revealed the gas distribution law in the gob,which provides theoretical basis for further proposing the comprehensive gas management technology.This will provide a theoretical basis for further proposed gas management technology.(3)Under the condition of Y-type ventilation along the air stay lane,the air volume ratio control technology and buried pipe gas extraction technology in the gob were proposed.Using theoretical calculation and numerical simulation,the technical parameters of air volume ratio of main and auxiliary air inlet lane and buried pipe gas extraction in the gob under Y-type ventilation were optimized,and the air volume ratio of main and auxiliary air inlet lane was determined as 3:1,the spacing of buried pipe in the gob is 40m and the height of buried pipe is 1.5m.(4)Based on the above research content to carry out field industrial test,test data show that:Y type ventilation under the main and auxiliary into the wind tunnel air ratio3:1 than 2:1 and 4:1,the gas concentration at each measurement point of the mining field is lower,gas management effect is more obvious;mining empty area buried pipe extraction negative pressure the greater the gas management effect is better,determine buried pipe extraction negative pressure for 30k Pa.gas overall management effect is:after the rack mining empty area and The overall effect of gas management is:the gas in the back of the frame gob and the gas in the corner of the return wind dropped 73%and 64.6%respectively,the gas concentration in the working face was kept within the specified concentration range,the gas concentration in the return wind lane never exceeded the limit,the average total air supply in the main and auxiliary inlet lane is reduced 182m~3/min,the overall effect of gas management is good.This thesis has a total of 57 figures,17 tables,and 96 references.