Study On Multiple Pressure Relief Effect And Relief Methane Drainage In Coal Seam Group Exploitation

The Multiple Pressure Relief Effect is an objective phenomenon which creates aprofound influence on the gas extraction in the exploitation process of theshort-distance coal seams. This thesis has systematically summarized the current studysituation of the pressure relief mechanism, the migrational law of the disposed methaneand the relieved gas extraction in the exploitation of the protective coal seam.Combined with the practical exploitation of the11223and the111811working surfacesof Jinjia Coal Mine, it makes a comprehensive study of the multiple pressure reliefeffect and the relief methane drainage technology for multiple protective coal seams’exploitation by using theoretical analysis, numerical simulation, on-spot measurement,etc.By adopting the knowledge of the elastic-plastic mechanics, this thesis establishesa mechanical model of the surrounding rock after the exploitation of the protectivecoal seam, which analyzes the variation law of the stress, the change of thedisplacement of the overlying and the underlying rock layers, and explores thecompound pressure-release effect on the exploitation of the multiple-protective coalseams from theoretical aspects.Combined with the engineering geological condition of Jinjia Coal Mine, thisthesis employs the numerical simulation software FLAC3Dto make a numericalsimulation for the first and the second protective coal seams’ exploitation respectively,gets some information about the vertical stress change, displacement and thedistribution of the plastic zone on the overlying protected coal strata.It analyses theforming process and the distribution features of the multiple discharging pressureeffect during the exploitation of the coal seam group.Based on those studies, this thesis analyses the migration law of the discharging pressure gas on the protective layers, the formation mechanism of the gas migrationgallery and the assembling zone of the discharging pressure gas; discusses the methodsand the flow of separate source predicted on multiple protective layers, the source ofthe gas during the exploitation of the second protective layer in Jinjia Coal Mine andcalculates the gushing amount of gas from different places.According to the specific conditions of Jinjia Coal Mine, this thesis puts forwardsfour kinds of methane extraction methods, namely, drilling holes upwards anddownwards the protective coal seam, high-field drilling holes in the return airway,buring tubes in the return airway and with the high drainage roadway to conveys anextraction of the disposed methane on the second protective coal seam which has beenexploited. And therefore, tt designs the specific implementation plan of the methaneextraction in111811working face and makes industrial tests as well as extractioneffect inspection on them.The spot engineering test of Jinjia Coal Mine shows that the greatest amount ofthe methane drainage is located in the high drainage roadway11223and the tube-buried return airway111811,which amounts to34.41percent and30.73percent of thetotal volume respectively. The most condensed methane drainage is located in theclosed lane of the high drainage roadway11223and the high location drilling of thereturn airway111811, the average concentration of each achieves9.88percent and12.19percent respectively, the methane density on the working face keeps in the rangeof0.225percent to0.446, and gas extraction rate keeps in the range of76.33percent to86.77,the general effect of the methane drainage is excellent.