Effect of diurnal fluctuation of atmospheric pressure on gas migration in goaf of coal mine

The atmospheric pressure fluctuation will break the pressure balance between the goaf and the working face, and the phenomenon of goaf breathing will occur. The breath causes the regular gas flow out or in between the goaf and the working face, which results in the migration and exchange of the fresh air in the working face and the poisonous and harmful gas in the goaf. Therefore, the risk of disaster in goaf is increased. In this study, based on No.16-17-22050 of Pingdingshan Tian'an No. 9 Coal Mine Co., Ltd, a large number of CFD simulations were carried out by using different fluctuation amplitudes to analyze the influence of diurnal fluctuation of atmospheric pressure on gas migration in goaf. The simulation results show that the goaf is like a semi-closed accumulator. When the atmospheric pressure increases, the increase of inlet flow leads to the accumulation of energy in the goaf, which leads to the farther the spontaneous combustion hazard zone (SCHZ) from the working face and the decrease of methane concentration in the return air corner. When the atmospheric pressure decreases, the decrease of the inlet flow causes the energy release in the goaf, resulting in the closer distance between SCHZ and the working face and the higher methane concentration in the return air corner. The size of SCHZ increases due to atmospheric pressure fluctuation. The above findings provide a theoretical basis for coal spontaneous combustion fire prevention and goaf methane disaster control.