Abstract: To investigate the mechanisms of rockburst and to explain the process of rockburst occurrence, a two-body model of the ejection rockburst source was proposed by analysing the sources, the dissipation and the magnitude of the released energy. The rockburst is essentially a process of brittle crack growth and rapid energy release in rocks under the interaction between energy- release-body and rockburst-body. Based on the tensile fracture mechanism of rockburst-body, the influence of crack spacing and strain rate on the dynamic energy release rate was analysed by using a dynamic model of brittle cohesive crack-array growth. The role of energy-release-body for rockburst-body can be attributed to loading strain rate effect. It can be found that a higher energy release rate of energy-release-body results in a greater dynamic loading rate and energy release rate of rockburst-body. Meanwhile, a higher energy release rate of rockburst-body leads to a greater dynamic discharge rate and energy release rate of energy-release-body. Dynamic loading and unloading effect caused by the interaction between two bodies constitutes a positive feedback mechanism of rockburst energy release. Based on the above theory, it is concluded that the geometrical scale of the rockburst source is almost several to dozens of times larger than rockburst-body, which is consistent with the field monitoring results.

Key words: ejection rockburst, two-body system, dynamic crack propagation, energy release rate, strain rate effect, geometric scale