A novel technique for temporal evolution of rockburst in underground rock tunnel: an experimental study

In this research, a series of tunnel physical models were tested under compression to predict the rockburst hazard through the analysis of fracture propagation patterns. The acoustic emission (AE) sensors were attached to the specimens to detect the crack damage. During the tests, the applied load, acoustic signals and failure pattern transitions were carefully recorded. Due to the closure and rubbing of pre-existing fractures, a considerable number of AE events were created in the early stage of loading, resulting in a high seismic "Ib value". As loading progressed, small rock particles were violently ejected from the tunnel sidewalls and cracks were started appearing. In all the tests it was observed that just seconds before the failure, the Ib value decreases sharply. The seismic "Ib value" and the energy released by the specimen during loading are inversely related. The decrease of "Ib value" can be considered as the precursor to predict the rockburst event.