Abstract：Based on the basic theory of coal-rock deformation and gas flow in coal and rock formations，considering the heterogeneity of the coal-rock，the nonlinear variation characteristics of gas permeability，and the coupled fluid-solid interaction between gas flow and solid deformation during the coal-rock deformation and failure process，a numerical model(RFPA2D–Flow) on coupled gas flow in coal-rock formations during the failure process of gassy coal-rock is established；and the numerical solution method for the model is also presented. Then，using the RFPA2D–Flow code，the catastrophic delay outburst of coal and gas induced by cross-cutting underground coal mine is numerically modeled to investigate the mechanism of coal and gas outbursts. The numerical simulations reproduce the whole process of the initiation，propagation，interaction，coalescence of the microcracks under the combined action of gas pressure，in-situ stress，and physical and mechanical properties of coal-rock. It is indicated that delay outbursts together with instantaneous outbursts are both caused by combined action of gas pressure，in-situ stress and physical and mechanical properties of coal-rock；and the outbursts process can be subdivided into four phases，namely，stress concentration stage，coal-rock fracturing and splitting induced by the combinations of gas pressure and in-situ stress，cracks propagation driven by gas pressure and the abrupt ejection of coal and gas. And so，it offers some theoretical basis and evidence to further investigate the mechanisms of gas drainage to prevent the occurrence of coal and gas outbursts in underground collieries.
