Mechanism of multifield coupling-induced outburst in mining-disturbed coal seam

Abstract

Coal and gas outburst is a typical dynamic disaster occurring during coal mining. To analyze its multi-field coupling mechanism, in this study, a multi-field (including coal stress field, damage field, gas diffusion field and seepage field) coupling model was established based on the heterogeneity of coal, and the mining process of horizontal and coal seam with fault were numerically simulated. Besides, the evolution of gas pressure, von mises stress and permeability under different parameters were analyzed. The results show that the stress relief zone in front of the working face is damaged by the mining disturbance, and the permeability increases sharply due to the full development of internal fractures. The coal in the stress concentration zone is affected by the stress concentration, which leads to the closure of fracture and the sharp decrease of permeability. As a result, the gas pressure gradient between stress relief zone and stress concentration zone increases, thus raising the risk of coal and gas outburst. The front geological structure of working face leads to the formation of multiple stress concentration zones in the coal seam, and the risk of coal and gas outburst increases with the increase of overburden stress. Based on the interaction between geological structure, gas pressure, coal mechanical properties and overburden stress, the mechanism of coal and gas outburst can be revealed. The research results can provide theoretical guidance for disaster prevention of coal and gas outburst.