The first of two TBMs on the North-South bypass in Brisbane, Australia, holed through last month to complete its 4.3km long drive, and its sister shield is due to finish the twin tunnel by early next month.
Launched in March last year, the 12.34m diameter double shield gripper – S-376, and named “Florence” – advanced 20m per day on average. The launch site was at Bowen Hills and the shield holed through at Kangaroo Point in early December, leaving the 1.5km long second, and last, section to drive to Woolloongabba.
Geology along the alignment comprises mainly tuff (80MPa-150MPa) with some arenites, phyllite with quartz veins, and faulted rock. The cover to the main tunnels varies from 6m to 30m. The contractor encountered less water than expected when passing below the river, T&TI was told.
Contractor on the project is LBB JV, a partnership of Leighton Contractors, Baulderstone Hornibrook and Bilfinger Berger. The JV has a fixed time and cost design and construct (D&C) contract with concessionaire RiverCity Motorway to build the 6.8km long North-South Bypass.
The sister Herrenknecht shield– S-375, or “Matilda” – had less than 800m left to bore in mid-April. The TBM was launched on its first, 2.5km long, drive in December 2007 and holed through at Kangaroo Point in January, shortly after Florence. The TBMs will be dismantled and returned to the manufacturer.
The main tunnels, which run up to 60m below Brisbane river, were renamed Clem Jones Tunnel (“Clem7”) during the construction phase. Each tube of the toll route will carry two lanes plus safety shoulders.
Tunnel design was performed by Bilfinger. The geotechnical work was done by Golder Associates (T&TI, July 2008, p25-27).
Tunnelling work has also involved seven roadheaders for the access and slip road bores plus a short part of the main tubes, the majority of which – 90% – are being excavated by the TBMs.
Production of the 38,000 segments for the tunnels was completed in late March having started in August 2007. The average production rate for the 400mm thick, 2m wide segments over the period was 100 units per day. The precast production plant was supplied by Euroform, and the steel reinforcement fabrication plant for the segments by AWM.
More than 50 of the 60 cross passages and substation passages have been excavated.
First tunnel bore completion at Clem7, Brisbane
