Quantitative assessment of energy changes in underground coal excavations using numerical approach

Coal burst is caused by a dynamic and unstable release of energy within the overstressed rock mass/coal during the mining process.Although the occurrence of coal burst is a result of the complex impacts of many factors,a major component of coal burst mechanism is associated with energy storage and release.This study reviewed the sources of energy that can contribute to a coal burst,principally strain and potential energy stored in the coal mass around excavations,and radiated seismic energy released by geological discontinuities.The energy balance concept proposed by[1]was utilised in numerical modellings to compute the radiated seismic energy in a modelling system and the kinetic energy of ejected rock/coal for a given burst scenario.The modelling results showed that the strain energy density(SED)around excavations increases with increasing mining depth and the maximum SED area migrates deeper into the coal.For the effect of geological features on both roadway and longwall face,the coal burst risk proneness can be assessed considering the proposed energy terms.According to the results of energy changes in excavations,the modelling predicts that for depths of ejection 2 m and 3 m the kinetic energy of a burst increases as the mining depth increases from 100 m to 1000 m,but for depth of ejection 1 m only increases until mining depth reaches 700 m and then decreases.The proposed energy-based model indicators can deepen the understanding of energy changes and the associated coal burst risks for different mining conditions.