Investigation of methane-air explosions and its destruction at longwall coalface in underground coalmines

Abstract

ABSTRACT Methane-air explosions are the most fatal accidents in underground coalmines. To understand its destruction, a worst-case full-scale methane-air explosion at a longwall coalface was simulated and analyzed based on accident investigations. It was found the flame covers a short length with an expansion ratio of about 6.67 at the longwall coalface, and crosscuts reduce the ratio to 3.67. Bifurcation reduces the peak overpressure by 25%–32% and the peak velocity of blast waves by 18.5%–23.5%. Corners have a significant effect on mitigating the peak overpressure but have a negligible impact on the blast velocity. In a long straight tunnel, the peak overpressure and blast velocity decay slowly and linearly by just 18.5% and 17.3%. A high-speed blast wave with debris and toxic and anoxic airflows at a velocity higher than 100 m/s were obtained from the accident investigations and in most of the simulation domain, it is the biggest challenge to evacuation and the most destructive force at the far-field disaster areas of methane-air explosions in underground coalmines. Thus, crosscuts, corners and blast velocity retarding methods should be more adopted to mitigate explosions and improve the rescue and evacuation safety.