ABSTRACT
The intensity of a rock burst event is associated with the excess strain energy released from the ejected rock, the energy released from the surrounding rock and the energy of the seismic waves in the case that the burst event is triggered by a fault slippage nearby. The transformations of the energy in a rockburst event are analyzed in this paper. Three energy resources exist when a burst event occurs: the strain energy stored in the rock to be ejected, the energy released from the surrounding rock and seismic energy. All the three types of energy are transformed to fracture energy to damage the rock and kinetic energy to eject the rock during bursting. The energy transforms are first illustrated in a conceptual model. A circular tunnel is taken as an example to demonstrate the relationships of the released energies with the burst depth. Finally, quantitative relationships are established between the ejection velocity of the rock and the released energies. The study shows that the intensity of rockburst is related to the excess energy released for the ejected rock, the burst depth and the magnitude of the seismic event. The intensity of a strain is mainly dependent on the excess energy in the case of a shallow burst, but the role of the energy released from the surrounding rock becomes important when the burst depth is large.
