9.8 km x 10 m-diameter tailrace being driven by Robbins TBM equipped with 68 x 432 mm front/back loading disc cutters suited to rock hardness to 200 MPa. Gneisses, quartzites, gabbros, amphibolites and granites expected with faults, blocky conditions and water inflows. Maximum cover 1,220 m. Contracting jv of Fletcher, Dillingham and Ilbau. Value US$ 85 million. TBM operations commenced mid-1998 with support generally comprising rockbolts, mesh and shotcrete. Dec 1998.
Robbins 10 m-diameter hardrock TBM with flat, narrow cutterhead driven by eleven 2-speed electric motors offering torques of 6,300 kNm at 5 rev/min and 9,500 kNm at 2.5 rev/min and total power of 3,500 kW. High-capacity three-axis type main bearing. Cutterhead dressed with 68 x 432 mm disc cutters rated at 267 kN which can be front or back loaded. Ring beam erector and equipment for grouting, roofbolting, spiling and drainage mounted on machine. Rates of up to 30 m/day reported with completion planned for October, 2000. May 1999.
www.southernlakes.co.nz/2mtt/2mtt.htm
During late August, 1999 the TBM passed the 3 km mark and intercepted and crossed the third major fault. Groundwater flows have remained constant at a total of 475 l/sec while water pressures in the probeholes ahead of the TBM are as high as 38 bar. All six permanent pumps have been installed in the dewatering complex and are available if needed. Visit www.robbinstbm.com for more information about the face machine. November 1999.
Aquatic Sciences Inc reports that has been awarded a challenging underwater tunnel inspection for Meridian Energy Limited, New Zealand at Manapouri. An underwater remotely operated vehicle will conduct an internal sonar and video inspection of the existing 9.8 km tailrace tunnel to survey structural conditions. The shutdown period for the inspection procedure to 48 hours, and no dewatering is necessary. The ROV is tethered by a sophisticated umbilical that transmits sonar and video data real-time to the surface via fibre optic telemetry.
ASI has completed continuous surveys of 10 km from a single access point using this robotic system, including inspections of a 120 km water supply tunnel in Finland. More from www.aquaticsciences.com March 2000.
Breakthrough of Robbins TBM reported midnight on 13th March, 2001 can be viewed at www.tunnelcam.co.nz and visit www.robbinstbm.com 12/01.
