| With the development of coal seam to the deep,coal seam with low permeability,high gas pressure and high ground stress seriously increase the difficulty of pressure relief mining,reducing the effect of gas extraction,and the protective layer is enhanced pressure relief to improve gas extraction effect One of the main methods.In this paper,we focus on the mining of coal outcrops in the near coal group,and use the theoretical analysis,the similar material physical simulation experiment and the numerical simulation to study the effect of the protective layer on the protective layer under repeated mining conditions The Law of Variation of Gas Seepage after Pressure.Through the independent design of the experimental system and experimental methods to carry out a similar material physical simulation experiments,combined with the iMPact of the iMPact of seepage analysis of the theoretical analysis of the protective layer of the protective layer of the gas flow in the protective layer of regular changes in the experimental results of the analysis The permeability curve of the whole process is hump-like,and the permeability is reduced,increased,decreased and stabilized in the process of advancing.With the increase of the number of protective layers,the layer spacing with the protective layer The smaller the permeability of the protective layer.The three-dimensional mathematical model of multi-layer protective layer was established by using FLAC3D numerical simulation software.The depressurization characteristics of the protective layer and the damage degree of the bottom plate were simulated.After the protective layer was completely stable,The pressure curve shows the opposite of the permeability curve of the hump,mining multi-layer protective layer,the protective layer is more fully depressurized,the deeper the floor damage,the greater the degree of damage.Based on the numerical simulation and physical similarity simulation,the variation law of seepage flow in the different stress area of the bottom plate is obtained according to the law of stress change on the floor.The seepage of the protective layer is changed by regional variation.The pressure expansion zone is enhanced by increasing pressure,and the seepage is greater than the original stress region,and the main reason of seepage is obtained with the increase of the number of layers.This paper provides a theoretical basis for optimizing the layout of the gas drainage system and improving the pressure relief effect and the gas extraction rate. |
