Study On Seepage Law And Application Of Long-distance Lower Protective Seam Mining

With the development of coal seam to the deep,the coal seam with low permeability,high gas pressure and high ground stress seriously increase the difficulty of pressure relief mining and reduce the effect of gas extraction,and demanding higher requirements for outburst prevention measures such as protective layer mining technology.In this paper,theoretical analysis,physical simulation experiments of similar materials,and numerical simulation methods are combined to systematically study the law of pressure relief and deformation of coal rock mass under long-distance protection,the evolution law of gas permeability,and the three-dimensional gas drainage system.From the experimental study,it is found that the unloading effect of the protected layer is different due to the different mining distance in a long distance lower protective layer,resulting in a regular change of the deformation rate and permeability.As the working face is gradually forward,the stress change of the protected layer has experienced 5 stages,the stress of the original rock,the increase of stress,the decrease of stress,the recovery of stress and the restoration of stability,the overall maximum principal stress is "W" shaped;the coal seam has also experienced the original deformation and compression deformation,expansion deformation,recovery,recovery and stable deformation,deformation rate was "M" shaped distribution,the penetration is experienced by the original permeability,reducing infiltration flow,pressure relief sufficiently high transparency and high flow,pressure recovery reduction through reduced flow,permeability to restore balance in 5 stages,in the direction of working face,the permeability change curve was "saddle".At the same time,it also shows that,under the long distance condition,the protective layer in the curved subsidence zone has the "O" ring distribution in the protected layer after the protective layer was mined.The decompression gas drainage in the protected layer needs to consider the effect of protective layer mining on the law of pressure relief of the protected layer and the time-space relationship between the two.Based on the law of pressure relief gas seepage in the lower protective layer and the influence factors of the spatial stability of the bottom Lane extraction,taking a mine in Henan as the research background,reasonably determine the position of the bottom extraction tunnel and the drilling layout parameters,and use the amount of gas drainage as the inspection basis.The results show that during the mining process of the long-distance lower protective layer,the pressure relief of the protected layer is sufficient,the fissures develop,and the seepage flow increases.On top of that,with scientific pressure relief gas drainage technology,coal seam gas outburst can be effectively prevented.