Mechanism of the delayed coal–gas outburst caused by creep instability of the ‘‘barrier layer and tectonic coal’’ combination

Abstract

A delayed coal–gas outburst incident often represents a more severe threat to health and safety of mine personnel than an instantaneous coal–gas outburst incident. For a better understanding of mechanism of the delayed coal–gas outburst, structure of “barrier layer and tectonic coal” combination in the delayed coal–gas outburst is firstly introduced in this paper. Based on, the delayed coal–gas outburst under different conditions of mining depth and thickness of the barrier layer are numerically simulated. Results indicate that the barrier layer enters the tertiary creep stage in a shorter time as mining depth increases and as thickness of the barrier layer decreases. Then we analyze effect of dynamic disturbance on the delayed coal–gas outburst. Our enquires reveal that 92.31% of the delayed coal–gas outburst incidents in China from 2011 to 2020 were affected by dynamic disturbance within 10 days before their occurrence. It is also proved that presence of dynamic disturbance makes coal–gas outburst occur in advance. Finally, the creep instability model of the “barrier layer and tectonic coal’’ combination under dynamic disturbance is proposed, which reflects the comprehensive effect of four main factors: the ‘‘barrier layer and tectonic coal’’ combination structure, gas pressure, in-situ stress, and dynamic disturbance on the delayed coal–gas outburst, and thus can be useful for its prevention and control.