John Holland CPB Ghella JV hands over key section of Sydney Metro TSE works

Seen as one of the most complex tunnelling and excavation projects of recent times, the work included the construction of twin tunnels under Sydney Harbour and the permanent structure of the 30m-deep Barangaroo Station as part of the new Sydney Metro line.

The project included the deployment of five Herrenknecht tunnel boring machines (TBMs): four double-shield machines mined the route under the Sydney Central Business District toward the south west, excavating 14.5km of twin tubes with diameters of 6.96m. For the tunnel under the harbour, the JV chose a Herrenknecht Mixshield (‘Kathleen’) TBM for the heterogeneous geology and high water pressure. The machine mined 900m-long twin tubes of 7.04m diameter.

Also included in the project were:

• Two permanent dive portals, also used to launch TBMs at either end of the alignment, at Chatswood and Marrickville.
• Access shafts at each of the three mined stations at Victoria Cross, Martin Place and Pitt Street to facilitate excavation and permanent lining of the station caverns.
• Three open-cut stations at Crow’s Nest, Barangaroo and Waterloo.
• A fully concrete-lined crossover cavern at Barangaroo that involved the removal of 650,000t of crushed rock (equivalent to 1,650 Airbus planes).
• 57 cross passages at 240m intervals.
• A temporary retrieval shaft at Blues Point, on the north side of the harbour, for the two TBMs that completed the northern drives, as well as the under harbour TBM.
• The use of barges to remove crushed rock from Barangaroo and Blues Point.
• Heritage excavations at five sites, uncovering items from Sydney’s early history, and
• A precast facility at Marrickville which produced 99,000 tunnel lining segments.

Sydney Metro City & Southwest will extend the new metro network from the end of Sydney Metro Northwest at Chatswood, under Sydney Harbour, through new railway stations in the CBD and west to Bankstown – a total of 66km of metro line.

Trains will start running through the harbour tunnels in 2024, extending to the North West Metro, into the city and beyond to Bankstown.