Formation of methane hazard in longwall coal mines with increasingly higher production capacity

Increasingly higher hard coal production capacity in Upper Silesian Coal Basin (Poland) in the last two decades led to significant increase of methane hazard occurrence in the workings of exploitation areas. An increase of methane content in the exploited seams and in the surrounding strata, associated with increasing depth of mining, results in higher methane emission into the longwall areas from exploited seams and degassing seams in the mining-induced de-stressed zone. Operational experience gained by the collieries confirms that reducing methane release during longwall operations often requires decreasing operating speed of a shearer in a shift. The paper presents an analysis of the parameters and factors, which have critical influence on the formation of methane hazard in longwall areas with high production capacity.