Effects of structural planes on rockburst position with respect to tunnel cross-sections: a case study involving a railway tunnel in China

Uncertainty in the locations where rockbursts may occur with respect to a tunnel cross-section greatly increases the difficulty in monitoring and providing warnings of rockbursts and mitigating their effects. In this paper, we analyze the characteristics of 40 rockbursts that occurred in a railway tunnel in China. The rockbursts are divided into three cases depending on their position with respect to the tunnel cross-section and the prevailing geological conditions. An in situ microseismic (MS) monitoring system was established to determine the likely position of rockbursts with respect to tunnel cross-sections. The spatiotemporal evolution of the MS events that occurred during the development of rockbursts belonging to the three cases was subsequently obtained. The mechanism responsible for the changing positions of rockbursts with respect to tunnel cross-sections was further elucidated by analyzing the fracture type of the MS events and conducting numerical simulations using three-dimensional distinct element code (3DEC). Finally, support schemes, based on the monitoring and simulation results, are suggested.