Mechanism And Application Of Roof Cutting And Pressure Relief By Hard Roof Blasting In 15216 Working Face Of Yuxing Coal Industry

The caving step distance of thick and hard roof is large,especially under the mining condition of thick coal seam,the ground pressure behavior of hard roof working face is strong,which is easy to cause accidents such as support pressing.Yuxing coal industry mainly Mines coal seam 15.The average thickness of the coal seam is about4.5m,and its basic roof is limestone with an average thickness of 10.33 m.Taking 15216 face as the research background,using the research methods of theoretical analysis and numerical simulation,this paper mastered the law of the first and periodic pressure step of the roof of the working face,determined the key technical parameters of pressure relief by roof cutting blasting,carried out industrial tests on the site,and achieved the following main results:(1)In order to solve the initial and periodic pressure step during the pressure coming of the working face,and considering the influence of roof cutting and pressure relief,the initial pressure step of the roof of 15216 working face is about 69 m and the periodic pressure step is about 28 m by using the theoretical model of "beam" and "plate".(2)The key technical parameters of roof cutting and pressure relief are determined by theoretical calculation,and the distribution law of overburden stress and plastic zone before and after roof cutting in 15216 working face is studied by numerical simulation.After the roof cutting and pressure relief of the working face,the deformation and stress of the roadway surrounding rock,especially the distribution area of high stress and large deformation,are significantly reduced.(3)According to the results of theoretical calculation and numerical simulation,and combined with the on-site engineering geological conditions,the blasting top cutting technical parameters of 15216 working face are determined: the vertical height of blasting top cutting is 7m,and the spacing of open cut holes is 4m;The distance between end blast holes is 12 M,the elevation angle is 45 °,the hole depth is 10 m,and the charge is 9.6 kg / hole;The blast hole spacing is 30 m,the elevation angle is 17 °,and the hole depth is 31 m.After adopting the deep hole blasting roof cutting pressure relief technology in15216 working face,the safe mining of the working face is realized and good technical and economic results are obtained.