Abstract: Coal bumps have been a major safety concern in underground coal mines in China for more than fifty years. In general, a coal bump refers to a sudden and violent failure of a coal seam that releases contained elastic energy and expels a large amount of coal and rock into the roadway or working face where men and machinery are present. It can cause fatality, injury and significant economic loss for the coal mining industry. Coal bumps occur more frequently in an island longwall panel, which is surrounded by previously mined panels, than in other longwall panels because of its high-stress concentration. In order to investigate the suddenly release of strain energy during extraction of mining face, the nonhomogeneity of materials will be considered to understand the mechanism of energy explosion during periodic weighting of the island longwall panel. Numerical simulations were conducted to study the dynamical character of elastic strain energy relief based on the geological conditions of T2193B island longwall panel in the Tangshan coal mine. Numerical results suggest that the constant collapse of immediate roof will cause continuously increasing of the main roof suspension. Meanwhile, the accumulated elastic strain energy in main roof will abruptly release when the periodic weighting occurs. At this moment, the coal bumps will occur more frequently in the mining face and roadways. It can be revealed that elastic strain energy explosion of main roof and coal seam during periodic weighting is considered to be an important precursor of coal bump occurrence during the extraction of an island longwall panel. Therefore, the significant reason of occurrence of coal bump is the suddenly elastic strain energy explosion during the periodic weighting of man roof. This study of coal bumps in the island longwall panel is of significant importance for coal mine safety and productivity.

Key words: island longwall panel, coal bump, elastic strain energy, periodic weighting, numerical simulation