Characteristics of depressurized fissure and its effect on deformation induced pressure relief of mining coal mass containing gas

The characteristics of fissure induced pressure-relief at different gas pressures and its effect on deformation induced press relief of mining coal mass containing gas were analyzed by using FLAC software.A strain-softening constitutive relation was used and the confining pressure was unloaded after the model reaching a static equilibrium state.The numerical results show that the peak stress and its corresponding axial strain of damage failure and the descend amplitude after peak stress decrease,with the rising gas pressure,and the mechanical characteristics become brittle from plastic.The supporting capacity of coal mass containing gas decreases with the rising gas pressure,and the tensile failure appeared ahead caused by increasing stress in effective stress space.The depressurized deformation and failure area induced pressure relief are larger with higher the gas pressures at the same confining pressure,and the characteristics of fissure induced pressure relief are more obvious,which caused the peak stress rising and its location away from the pillar longer.When the gas pressure reaches a certain value,the effect of gas pressures on the depressurized deformation of mining coal mass containing gas cannot be neglected.