Numerical simulation on multiphysics field distribution characteristics of coal and gas outburst

In order to reveal the mechanism of multiphysics field coupling catastrophe of coal and gas outburst, based on the gas-solid coupling equation of gas-containing coal, the solid mechanics and PDE modules in the COMSOL software were used to simulate the distribution law of coal stress field, deformation field and gas flow field before and after outburst.Compared with the results of outburst physical simulation experiments carried out in the early stage, the feasibility of the numerical analysis method was confirmed. The simulation results show that the plastic deformation of the coal mass near the wall of the hole after outburst causes the permeability increase, and with the increase of stress, the permeability at the wall of outburst hole can be increased by 2 to 3 orders of magnitude from the original value; from the wall surface of outburst hole to the deep part of the coal mass, the gas pressure shows a tendency to rise sharply and then decreases to the original pressure when the outburst occurs. The formation of higher pressure gradient at the wall of hole is a necessary condition for the continuous occurrence of outburst.