Rock-burst is a local instability problem affecting compact rock-masses in deep tunnels: it can generate important over-breaks, but even more, safety issues for workers in the area where it occurs. The experimental study, aimed at predicting rock-burst occurrence during the excavation of the Brenner Base Tunnel, was carried out in massive granite below an overburden of 1000-1200 m.
Risk associated to rock-burst occurrence in tunnels is nowadays managed by a continuous monitoring of acoustic emissions recorded during the excavation, whose characteristics depend on the failure processes ongoing in the rock-mass. A new in situ test was specifically designed with the aim of calibrating the alarm threshold for rock-burst occurrence. The test consists in compressing to failure a portion of the rock-mass at the tunnel side-wall by means of a couple of flat-jacks, measuring simultaneously the generated acoustic emissions with accelerometers.
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