Robbins TBM rolls into hard rock history May 2011
Desiree Willis, Technical Writer, The Robbins Company
- When the Robbins main beam gripper TBM broke through at Niagara it entered the international TBM record books. On 13 May this year, the world's largest hard rock TBM completed the 10km long water diversion tunnel to increase output of the Ontario Power Generation company's Sir Adam Beck hydropower plant.
- The massive 14.4m (47.2ft) diameter mega machine was operated by tunneling contractor Strabag AG to cut the new tunnel from the sandstone that holds the Niagara River within its banks and above its famous falls. Following the historic breakthrough, the massive cutterhead is to be displayed in the city of Niagara Falls, Ontario as a monument to the efforts of the engineers and workers involved on the project and to the citizens of the city who have witnessed the advance of the project over the past five-and-a-half years.
Robbins Manager Mike Kolenich inspects the cutterhead
- The completion of the project comes after continuous highs and lows, from significant over-break to multiple world records. Challenging rock conditions in Queenston shale at the beginning of the TBM drive required the tunnel alignment to be raised by 45m into more stable rock. While in the difficult ground, crews undertook significant measures to safely scale down loose rock from the tunnel crown. After surmounting these conditions, the Robbins machine managed to achieve two records for any TBM of 11m (36ft) in diameter or larger - first a record of 468m or 1,535ft in one month, and secondly a record of 153m or 503ft in one week, both achieved during July 2009.
- "There is a tremendous sense of accomplishment here. There were huge logistical challenges just delivering and assembling the TBM onsite, and the machine has now overcome significant geologic challenges as well," said Mike Kolenich, Robbins Manager of Projects for Niagara.
- The project was initiated in June 2004 and the Robbins machine was launched in summer 2006 less than 12 months from contract signing, following Onsite First Time Assembly (OFTA). The project marked the first use of OFTA, which as a strategy saves both time and money to contractors compared to factory-assembled TBMs.
- The 14.4m o.d. tunnel drive is now being fully lined to a 12.8m i.d. diameter with a 600mm thick in-situ concrete lining. Once the inlet structure and control gates are in place, the cofferdam in the Niagara River and the rock plug at the outlet end of the tunnel will be removed to bring the new water delivery system into operation in 2013.
- Breakthrough ends troubled journey at Niagara - TunnelTalk, May 2011
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