Numerical investigation of two typical outbursts in development headings: A case study in a Chinese coalfield

Numerical modelling is an effective technique to improve the understanding of outburst initiation mechanisms and to take appropriate measures to address their threats. Based on the existing two-way sequential coupling method, two typical types of outbursts, i.e. the gas pocket outburst and the dynamic fracturing outburst, have been successfully simulated using field data from a coalfield in central China. The geological structure commonly observed in the coalfield, known as the 'bedding shear zone', contributes to the gas pocket outbursts in the region. The model for this type of outburst simulates mining-induced stress and gas pressure distributions during the outburst initiation stage and the subsequent development stage. Both coal ejection and gas release are observed in the model, and the simulation results are consistent with mine site observations, i.e. the amount of ejected coal, outburst cavity profile, and gas release rate change prior to an outburst. The second type of outburst is attributed to gas accumulation and elevated gas pressure due to the gassy floor seam and the heterogeneity in the floor strata, which is explained by the dynamic fracturing theory. While the dynamic coal ejection phenomenon is not captured in the simulation, the abrupt release of retained gas from a floor coal seam is successfully replicated. Both outburst models reveal that abnormal gas emission trends can be used as indicators of an upcoming outburst. The results of this study are expected to provide new insights into the outburst initiation mechanisms and outburst prevention measures.