It was well established that the deformation and final failure of rock and coal saturated with gases were accompanied by observable electromagnetic emission, and that electromagnetic field can change gas adsorption capacity of coal. Further investigation on latter may help improve understanding towards the mechanism of coal and gas outbursts and seek new techniques to prevent and control them. We investigated this phenomenon on a variety of coals saturated with gases. It is experimentally demonstrated that emission rate increase substantially when electromagnetic fields were applied to coal particles saturated with gas. The value of increase from outburst prone coal is greater than that from non-outburst prone coal. The observed results are explained in terms of pore structure difference between the two types of coals. Based on the theories of gas emission from coal particles and our experimental results, a new model for coal and gas outbursts is proposed, which can give satisfactory explanation to outburst phenomena observed in laboratories and in situ. Moreover, this model clarifies the unique role of fracture excited electromagnetic emission in initiation and development of an outburst. New ideas to prevent and control outburst are suggested according to the new model.
Coal and gas outburst problems have been exacerbated significantly over the past decade because of higher productivity and the trend towards recovery of deeper coal seams (Shepherd et al, 1981; Beamish et al, 1998). However, despite of great efforts, surprisingly little progress has been made towards understanding outburst mechanism (Litwiniszyn, 1990; He and Zhou, 1991; Krzesinska, 1997; Wang et al, 1998). Prediction techniques continue to be unreliable and unexpected outburst incidents are still a major concern for underground coal mining. Nitsan(1977), Ogawa(1985), Yamada et al(1989), Rabinovitch et al(1998) and Frid et al(1999) observed electromagnetic emission accompanying failures of a variety of rocks.
