The Manapouri Tailrace Tunnel No. 2 construction - a very large TBM tunnel in very strong rock

摘要

The Manapouri Tailrace Tunnel No. 2 (2MTT), located in southern New Zealand, was constructed between 1997 and 2002 as part of Meridian Energy, Ltd.'s 700 MW hydroelectric facility. The 10km long tunnel is one of the World's largest full face TBM tunnels, at 10m diameter, driven in strong to very strong rock. Many obstacles were traversed by the contractor. The TBM passed through five major fault zones, 5 to 120 m wide with cumulative groundwater flows up to 1,0001/s; however, the most difficult ground for the TBM was the hard, blocky ground. This project pushed the envelope in hard rock TBM tunneling due to tunnel size, water inflows, the strength of rock, environmental considerations, and the isolated nature of the site. Construction difficulties and ensuring contractor claims resulted in exhaustive studies of rock properties and TBM behavior which now provide important insight into hard rock boreability.