Successful end for trouble-hit subsea drive
20 Feb 2014
Thiess News Release
- A milestone in the 430km-long Santos Gas Transmission Pipeline Project in Australia is reached following completion of the marine crossing under the Narrows for connection with Curtis Island off the northeast coast of Queensland, Australia.
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Thiess construction team celebrates breakthrough on Curtis Island
- Breakthrough into the reception shaft on Curtis Island earlier this month (February) follows a challenging drive during which the refurbished 4.05m diameter Herrenknecht EPBM selected for the project suffered cutterhead damage.
- "I cannot speak highly enough of the team and what they have achieved, particularly in the last couple of months when the geotechnical conditions got very tough," said Steve Wille, General Manager Tunnelling for the tunnel contractor, Thiess.
- "Tunnelling had to stop for a few weeks mid-journey for the crew to repair the cutterhead, which was an extremely difficult and complex operation. To gain access workers had to operate under 2.4 bar compressed air pressure. It cannot be understated how difficult the conditions were for those guys and I'm extremely proud of the way they fixed the cutterhead and brought the machine home," said Wille.
- For the drive it was decided that an EPBM was best suited to the geological conditions that were expected, with a contingency to switch to open or slurry operation. The machine, which was refurbished, reassembled and commissioned by Herrenknecht at its facility in Brisbane, was previously used on a project in Victoria.
- Tunnel design incorporated injection of a cement-based grout to provide a permanent seal behind a 300mm thick precast segmental lining for a finished i.d. of 3.4m. A total of 21,750 segments were used along the 4.4km length of the tunnel.
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Fig 1. 430km pipeline to Curtis Island
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Fig 2. 4.4km tunnel alignment under The Narrows
- The completed tunnel is now being stripped of services and thoroughly cleaned, after which it will be flooded to provide buoyancy for the pipeline that is being installed by Saipem Australia.
- The multi billion dollar Santos gas transmission project is a JV between one of Australia's leading gas producers and three of the world's largest energy companies - Petronas, Total and Kogas. It involves transportation of coal seam gas from facilities in eastern Queensland (Fig 1) to a plant 430km away at Curtis Island near Gladstone on Australia's eastern coast, for liquefication and onward delivery to world markets. The Aust$134 million contract with Thiess for the subsea tunnel connection between the mainland and the LNG plant on Curtis Island (Fig 2) was awarded in September 2012 by the project's principal contractor, pipeline specialist Saipem.
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