Project Location :
Manapouri, New Zealand
Owner :
Meridian Energy, Ltd.
Design Firm :
Woodward Clyde and DesignPower of NZ
Contractor :
FDI (Fletcher-Dillingham-Ilbau)
Construction Manager :
-
Purpose of the Tunnel :
To optimize the efficiency of the existing tailrace system
Excavation Start :
June 12, 1998
Excavation End :
2001
Bid Value :
132,000,000 USD
General Geology :
Tunnel 2 is located within Paleozoic metamorphic provide access to the headworks from the existing and igneous rocks of the Fiordland Complex. The metamorphic rocks consist mainly of gneiss, calc-silicate and quartzite and the intrusive rocks are composed of Gabbro and diorite. Gneiss is expected for approximately 52% of the tunnel alignment. Mafic dykes and granitic intrusions intersect the formations as well. The ground is highly variable. Unconfined compressive strengths of the rock have been determined to be up to 226M Pa. The rock mass is fractured to varying degrees and eight subvertical fault zones are expected to cross the tunnel alignment with subvertical dip angles. The overburden varies between about 100 m at the portal to 1200m maximum. Total anticipated groundwater inflow is 1300 litters/s with the most significant inflows expected within the first 3.5-km of tunnel.
TBM Specifications :
Atlas Copco Robbins Model 323 –288
10.1-m cutterhead diameter
68 17-inch disc cutters with 0.75-inch tip with and 60,000 lbs max. cutter load
3465 kW cutterhead power
18156 kN (1816 tons) total installed thrust
Publications:
Heer B., Essex R., Young D., "Manapouri Second Tailrace Tunnel Design and Construction Considerations", RETC, Chapter 1, 1997.
New Zealand - Site Report, "Building the second Manapouri tailrace tunnel", Tunnels and Tunneling International, May 1999.
New Zealand - Site Report, "Manapouri struggles to make head way", Tunnels and Tunneling International, April 2000.
Martin T. F., Heer B., "Second Manapouri Tailrace Tunnel - Not just Another Walk in the Park", RETC 2003.