Numerical Simulation of the De-stressed Deformation of Mining Coal Strata at Different Pore Pressures

Gas extraction from mining induced de-stressed areas is one of the most efficient and cost-effective methods for eliminating coal and gas outbursts in China. In the paper, the characteristics of fracture induced pressure relief at different pore pressures and confining pressures on the de-stressed deformation of strata are analysed by using FLAC software. A strain-softening constitutive relation was used and the confining pressure was unloaded after the model was loaded to reach a static equilibrium state. The numerical results show that under the same confining pressure, and with the increase of pore pressure, the deformation of strata due to de-stressing as well as the fracture zones also increase significantly, and the characteristics of fissure induced pressure relief becomes more apparent. For seams with high gas pressure, the impact of pore pressure on the deformation of mining disturbed strata cannot be neglected. The numerical results are in good agreement with field observations, and improve the development of the coupled gas-solid theory in mining induced de-stressed strata.