ABSTRACT: Rockbursts in the tight confines of a TBM tunnel can be highly hazardous events given the proximity of vital equipment and workers to the rockburst source, and the space constraints that severely limit employment of countermeasures. Consequently, the ability to predict rockbursts with some measure of confidence as excavation proceeds (i.e. in the ‘short-term’) is critical to the safety of both workers and equipment. The Neelum Jhelum project in the Azad Kashmir region of northeast Pakistan, with twin 8.5 m diameter main-beam gripper TBMs operating under high horizontal stresses and overburdens up to 1,870 m, encountered rockbursts, prompting development of an investigative system to predict these events. The system relies on analysis of probing data, TBM boring parameters and above all, a sophisticated microseismic detection and analysis capability. Investigation techniques that failed to give useful results, or were not implemented for other reasons, are also discussed. To read the full paper please click here.

Jack Mierzejewski

Principal Engineer – Tunnels, Multiconsult AS, Norway.

Gary Peach

Resident Engineer –TBM, Multiconsult AS, Norway.

Bruce Ashcroft

Tunnel Engineer –TBM, Multiconsult AS, Norway.
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