Simulation investigation on flow behavior of gob gas by applying a newly developed FE software

Abstract

The fundamental understanding of migration characteristics of gob gas is essential for gas management to ensure safety and health during the longwall mining. Although many researches have been studying the gob gas flow and its control, the gob gas flow mechanisms are not well understood due to the lack of considering the in situ gob configuration and gas emission. Particularly, it is also pretty lack of convenient and practical software tools to characterize gob gas migration processes in longwall mining gobs. In this work, a coupled two-dimensional model, through fully considering dynamic porosity/permeability evolution, methane source emissions and gas flow during the continuous coalbed extraction, is proposed and implemented into a further-developed FE software. The FE model is validated by matching the in situ data well. Furthermore, it is applied to quantitatively evaluate the influence of longwall ventilation and mining parameters on the gas flow behavior of gob during the longwall mining. Simulation results show that the ventilation resistance and the longwall panel width parameters are positive correlation with the leakage flux and the return airway methane concentration; the larger the ventilation flux, the larger the leakage flux, but the smaller the methane concentration in the return airway; the higher advance rate corresponds to the higher methane concentration in the return airway, but it has a slight influence on the gob leakage.