Stress And Gas Pressure Of Coal And Rock Containing Gas Numerical Simulation Of Coupled Characteristics

In recent years,with the exhaustion of shallow coal mining in China,coal mines have entered deep mining,resulting in increased frequency and intensity of coal and gas dynamic disasters.It is mainly due to the disaster-causing factors of coal and gas dynamic disasters: stress and gas pressure change,which makes the mechanism of coal and gas dynamic disasters more complex.The study on the coupling characteristics of stress and gas pressure in gas-bearing coal and rock is the key to reveal the mechanism of coal and gas dynamic disasters and to prevent and control coal and gas dynamic disasters.However,the existing research on the coupling of stress and gas pressure in coal seams is mainly macro-qualitative.The quantitative laboratory test study replaces gas pressure in sealed sample tank with gas pressure in coal seams,so it is impossible to study stress and gas synchronously in real time.The essential relationship of pressure coupling.In order to further study the coupling characteristics of gas-bearing coal-rock stress and gas pressure,this paper simulates the coupling characteristics of gas-bearing coal-rock stress and gas pressure on the basis of laboratory and engineering scales.The following research results have been achieved:(1)Based on the pore characteristics and gas adsorption theory of gas-bearing coal and rock,the coupled constitutive equation of gas-bearing coal and rock stress and gas pressure is constructed according to Langmuir equation,the deformation field equation and seepage field equation of gas-bearing coal and rock based on the variation of gas pressure,stress,porosity and permeability of gas-bearing coal and rock.According to the coupling equation between stress and gas pressure of gas-bearing coal and rock,the laboratory test and numerical simulation of mechanical properties of gas-bearing coal and rock under different confining pressures are carried out,and the curves of stress-strain,porosity and permeability are obtained.According to the research,the porosity and permeability of gas-bearing coal and rock first decrease and then increase with the increase of stress,and the volumetric strain of gas-bearing coal and rock first increases with the increase of stress.Change law of big and then fall.According to the comparison between numerical simulation and laboratory test results,the conclusions are consistent,which shows the accuracy and reliability of the model..(2)Under different initial gas pressures and confining pressures,the mechanical characteristics of coal and rock containing gas were studied by numerical simulation.The results show that the porosity and permeability of gas-bearing coal decrease first and then increase with the increase of loading stress,whether the coal is under the same confining pressure and different initial gas pressure or under the same initial gas pressure and different confining pressure.The numerical simulation shows that the gas pressure in coal and rock changes in real time with the increase of stress,and the permeability and porosity of coal and rock.Before the compressive strength,the gas pressure in gas-bearing coal and rock increases with the increase of stress.When the stress exceeds the maximum pressure that coal can bear,the gas pressure in coal and rock decreases with the increase of stress.(3)Based on the field measured working face,the numerical simulation analysis is carried out.The numerical simulation shows that the pore gas pressure of gas-bearing coal increases first and then decreases with the increase of stress at different propulsion distances.The peak stress occurs at 15-25 m away from the working face,and the peak gas pressure occurs at 30-40 m away from the working face.And before the compressive strength,the gas-bearing coal stress and gas pressure show a positive correlation;when the stress increases more than the compressive strength of coal,gas pressure decreases with the increase of stress,and there is a negative correlation between the two.The numerical simulation results are in good agreement with the field observations.Figure [33] table [6] reference[61]...