Research On Pressure Relief Effects And Mechanism Of Mining Thickness Of Upper Protective Seam

Gas drainage is an important technical measure to prevent gas transfinite and gas disaster at work face.Because of the low permeability characteristics of coal seam gas storage conditions in China,It has great influence on the selection of gas drainage mode and the effect of gas drainage.In order to change the permeability of low permeability gassy coal seam in high gassy coal mine,improving the effect of gas disaster prevention and control,there are many technical measures to improve the permeability of coal seam.Mining the Protective Coal Seam is one of the most effective ways to increase coal seam permeability.The pressure relief effect of the upper protective coal seam mining affects the stress,deformation characteristics and permeability increase effect of the lower protected coal seam.To research the pressure relief effect of the upper protective coal seam is of great significance to formulate a reasonable plan of upper protective coal seam mining and improve the permeability of coal seam.The thesis uses theoretical analysis,similar material simulation,experiment numerical simulation and field test methods to studies the relief effect of upper protective coal seam mining.This thesis applies theoretical analysis to elaborate the pressure relief effect and main influencing factors of protective coal seam mining,obtain the influence of mining factors such as mining height,length of working face and spacing between layers on the pressure relief effect of protective seam mining,And the interaction relationship between the influencing factors,determined that the main factor affecting the pressure relief effect of protective coal seam mining is the mining height.The stress distribution characteristics of the floor under different mining hight are analyzed by using the similar material simulation experiment method,and the relationship between the mining height and the stress distribution of the floor and the evolution law is determined.Based on the theory of beam on elastic foundation and elastic mechanics,the stress distribution characteristics and influencing factors of the floor are analyzed,revealed the relationship between the mining height and the stress distribution of the floor,get distribution law of pressure relief value of floor under different mining height conditions in the stage of gob compaction stability.Based on the theory of gob compaction,application of FLAC3D numerical simulation software,simulation the upper protective coal seam mining under the conditions of different mining height,analysis of stress,deformation and failure characteristics of floor in mining process.The matching relationship between mining height,spatial position relation and protective coal seam mining efficiency is put forward.A method for determining effective spacing between layers is established under different mining height conditions.Based on the research results,the different mining height and corresponding effective interval of Hong yang No.3 coal mine are determined,when the height of the upper protective coal seam is lm,1.5m,2.0m,2.5m and 3.0m,the effective layer spacing is 0?29m,0?38m,0?43m,0?48m and 0?52m,and the interval between 3 coal protection coal seam and 7 coal seam is 48m.The height of the protection coal seam on the 3 coal is estimated to be 2.5m..