The Effect Of Pressure Relief Range Of Protective Layer Mining And Protection Research

By theoretical analysis, software simulation and field trials under the protection of the coal seam around the rock mass stress distribution on the protective layer mining conditions, coal bed expansion deformation characteristics and fractured, coal seam permeability variation and seam permeability coefficient optimization algorithm to carry out a systematic study and analysis of coal seam floor rock force, the establishment of the floor strata along the seam towards the mechanical model, in order to better qualitative and quantitative analysis of the distribution of characteristics of the backplane supporting force the model to do the appropriate simplified, and ultimately calculate the the floor stress distribution formula, summed up the stress distribution law of coal seam floor strata.Coal seam permeability coefficient was a important factor in protection layer mining and gas drainage.The main method to get the coefficient was drilling radial flow.The paper invest the relationship among coal seam permeability,time and flow rate combined with the principle and pictures.Finally,against the actual situation of the research work and management,the paper proposed two new methods to solve the permeability coefficient and analysis the time prospective number Fo and the discontinuity point in AB function.Relief effect,expansion and deformation characteristics and coal seam permeability variation of the protected coal seam were got through experiment.7a coal seam original gas pressure was1.9MPa and the original gas content was8.03m3/t,After mining8coal seam,7a coal seam residual gas pressure was0.3MPa and the residual gas pressure was2.64m3/t。After mining50208coal seam face out of the drilling hole40m,the amount of the deformation of7a coal seam was the biggest.The value was18.2mm and the tensile deformation rate was4.8%o.The gas drainage was2.9m3/min.Gas pumping rate of the relief region was75.6%.Permeability coefficient of7a coal seam was4.1057m2/MPa2·d,it was217times than original.The relief angle was60°along strike and75°along the dip. Within the scope f protection of8coal seam,the risk of8coal seam outburst was eliminated.Experiment results were consistent with the theoretical analysis and numerical simulation results.