Study On Overburden Fracture Evolution And Gas Migration In Goaf In Lower And Higher Drainage Roadway In Initial Mining Period

In recent years,with the increase of mining depth,coal mine gas disasters and a growing problem,particularly in working face gas emission during the preliminary extraction in the big,and the intensity of gas emission and the size of the gob roof caving is closely related to the intensity of the large area caving goaf roof and side end old pond caving for the first time a large number of high concentration of gas,can cause Angle,return on different levels of gas increases,or even cause gas warning overrun.Based on more than my coal goaf management mode for the engineering background,in view of the low smoke lane in application during the preliminary extraction in the difficulty for the engineering practice,conducted during the preliminary extraction in the working face with low smoke lane goaf flow field distribution of strata cranny evolution and research,through the analysis of the gas source analysis and field measurement,presents high alley pumping improvement scheme of arrangement,and cut and develop series of research,mainly the following results:(1)According to the analysis of gas emission rules of different fully mechanized caving working faces with field measured data,it is concluded that the gas emission in goaf occupies 48.67% of the total gas emission in fully mechanized caving working face at the highest level,and the gas extraction amount in high drainage roadway accounts for 97.07% of the total gas emission in goaf at the highest level.According to the geological conditions of N2103 fully mechanized caving working face of yuwu coal mine,roughly calculated caving zone height is 30.32 m and fracture zone height is 67.18 m.Numerical simulation software UDEC6.0 was used to carry out numerical simulation on the caving deformation law of overlying strata movement after the coal seam excavation of N2103 working face of yuwu coal mine,showing the generation and change process of overlying strata fracture field in different mining stages,and obtaining the movement deformation and failure law of overlying strata in different mining stages.(2)By comparing the effects of gas treatment in the initial mining period underdifferent communication modes of high drainage roadway and cutting hole,the layout mode of high drainage roadway with high drainage communication at the rear end is proposed.(3)Numerical simulation was carried out on the caving deformation law of overburden movement in the initial mining period of the working face through UDEC6.0,showing the generation and change process of overburden fracture field in different stages of the initial mining period,and obtaining the movement deformation and failure law of overburden in the initial mining period.According to the simulation results,the height of goaf caving zone is 32 m,and the height of fracture zone is 63 m,which is basically consistent with the calculated results.(4)By FLUENT software under different forward distance to face early mining stage to carry on the numerical simulation of goaf gas concentration distribution,the initial mining stage under different forward distance,high alley pumping in different vertical layers goaf gas concentration distribution rule and gas migration law,through comparative analysis summarizes the low drainage way for early stage mining goaf and the effect of gas control in the working face.