A new combination model for delay outburst of coal and gas

Sudden ejection of coal and gas in a delay outburst accident usually causes even heavier losses than an instantaneous outburst accident. A new combination model composed of outburst-prone soft coal and barrier layer was proposed to better categorise instantaneous outburst and delay outburst. The model offered an explanation for the delay outburst phenomenon, which demonstrates that it is the barrier layer between the work space and the soft coal that defers the occurrence of an outburst accident. Based on this model, delay outburst accidents in China from 2006 to 2016 were investigated. There were 42 delay outburst accidents resulting in 251 deaths, and the frequency of delay outburst accidents during operation of drilling accounted for 38.1%. Furthermore, the delay outburst process was numerically simulated. The simulations show that creep strain increases with the increase of stress, and gas pressure drops with increasing permeability of the barrier layer. [Received: September 30, 2017; Accepted: June 18, 2018]