Research On Mechanics And Seepage Law Of Gas-Bearing Coal-Rock Under Different Stress

In this paper,the research method of laboratory experiment,theoretical analysis and numerical simulation is used to carry out the research on the mechanics and seepage law of gas-bearing coal-rock,and the following research results are obtained:(1)Using YSSZ-500 A rock biaxial rheological tester,the uniaxial compression and acoustic emission experiments of coal seam roof rock samples were carried out,the acoustic emission characteristics of the rock during the uniaxial compression process were analyzed,and study the relationship between the damage variable and the axial strain of the specimen.(2)Experiments on mechanical and seepage characteristics of gas bearing coal samples and sandstone under different confining pressures are carried out.It is considered that with the increase of confining pressure,the strength of gas bearing coal and sandstone increases gradually,the relationship between coal strength and confining pressure is power function,and the relationship between sandstone strength and confining pressure is linear.The initial permeability of coal samples gradually decreases with the increase of confining pressure,and the permeability of sandstone only increases sharply after failure.With the increase of confining pressure,the permeability of sandstone gradually decreases after failure.(3)Aiming at the distribution law of in-situ stress near the N3012 working face in the Shamushu Coal Mine of Sichuan Coal Group,the evolution law of mining pressure in the 2+3# coal seam mining process was simulated and studied.Based on this,the stress loading and unloading paths in the X-Z,Y-Z,and X-Y directions are designed.Carry out research on the mechanics,deformation and permeability characteristics of gas-bearing coal under different stresses.At the same time,during the process of increasing axial pressure and unloading confining pressure,the principal stress difference of the coal sample gradually increases,but the ability of increasing axial pressure to close internal fissures is weaker than that of unloading confining pressure to open internal fissures,causing the permeability increases slowly with the increase of the principal stress difference.During the process of increasing axial pressure and confining pressure at the same time,the pores and cracks inside the coal sample are gradually closed under the action of axial pressure and confining pressure,and the permeability decreases nonlinearly with the decrease of the principal stress difference.(4)Analyzing the basic migration law of coal seam multi-physical field.Taking the N3012 working face as the engineering background,COMSOL software is used to simulate and study the characteristics of gas migration in coal by the spacing of the extraction holes.The gas pressure drop rate near the gas drainage orifice is the largest.As the distance from the gas drainage orifice increases,the gas pressure drop rate decreases slowly,but the rate of decrease gradually slows down.And the longer the drainage time,the greater the cumulative value of pressure drop around the hole,but the rate of increase gradually slows down.With the increase of gas drainage time,the rate of gas pressure drop around the borehole gradually slowed down,but the gas pressure at measuring point 2 in the middle of the two boreholes was lower than that at measuring point 1 where the drainage borehole was arranged on only one side.This shows that the more drill holes are arranged,the greater the gas pressure decrease.