A study on the energy sources and the role of the surrounding rock mass in strain burst

Abstract

Strain burst occurs within highly stressed hard rocks in underground excavations. A prerequisite for strain bursting is that excess energy exists to eject material after rock failure. Both the bursting rock and the surrounding rock mass will contribute to the excess energy. However, the proportion of the energy contributed from each is currently not well understood. This issue will be quantitatively investigated in this study. In this paper, the energy sources for strain bursting and the energy conversion during bursting are first illustrated in two conceptual models. The portions of the energy dissipated and released from the bursting rock and the surrounding rock mass are differentiated by means of numerical modeling. The numerical modeling shows that the proportion of energy released from the surrounding rock mass increases with increasing burst depth. Beyond a critical burst depth, the energy released from the surrounding rock mass becomes higher than the energy stored in the bursting rock. This concept was further verified by an analytical solution to the behavior of a circular opening when its radius is enlarged. Based on the study, it can be concluded that the magnitude of the burst is mainly determined by the strain energy released from the bursting rock itself in a shallow burst event, but it is more associated with the energy released from surrounding rock mass in a large scale burst event.