Research On Gas Distribution Law Under High Drainage Roadway And Buried Pipe Drainage In Goaf Of Yuwu Coal Industry

Yuwu Coal Mine as a highly gassy mine,its main mining 3# coal seam is characterized by low permeability and difficult drainage.Under the condition that fully mechanized caving is popularized and applied,the phenomena of high mining height,large gushing volume,excessive coal left in goaf and high gas concentration appeared in working face.The gas concentration especially in the upper corner,often exceeds the limit,which threatens the safety of production.Aiming at the above problems,this thesis taking N1101 working face as the research object,analyses the formation process of goaf on the basis of existing theory,including its spatial characteristics and the law of crack development and distribution.Based on the actual geological conditions of 3# coal seam,FLAC3 D is used to establish a model and simulate the advancing process of working face which shows the deformation and plastic failure of coal seam.In this way,the evolution mechanism of stress field and fissure field distribution in mining overburden is revealed.According to the seepage theory of porous media,this thesis analyses the law of gas occurrence,emission and movement in goaf.And based on the theoretical analysis and actual working conditions of working face,a three-dimensional CFD model of goaf is established.Then FLUENT was used to simulate the flow field and gas concentration distribution in goaf with "U" ventilation mode without extraction.The influence of air leakage on the flow field in goaf is comprehensively analyzed.At the same time,the reason of the gas concentration in the upper corner which exceeds the limit frequently is also discussed here.FLUENT was also used to study the influence of high-pumping roadway extraction and pre-buried riser extraction on the flow field and gas concentration in goaf.The extraction conditions of high extraction roadway under different vertical and horizontal distances and different buried pipe spacing are simulated respectively.And the influence of space position of high extraction roadway and buried pipe on extraction effect is analyzed which is helpful to summarize the discovery rules and get the best parameters of extraction layout.The validity and rationality of the extraction method are verified by the field measured data,which provides a reference method for the optimization of the gas extraction system in the goaf of Yuwu Coal Industry.