Melbourne metro celebrates new breakthrough

28 August 2020

Another breakthrough has occurred on Melbourne’s US$8bn Metro Tunnel project as TBM Joan emerged at Parkville station earlier this week. The machine broke through into the station box 20m below ground having mined 1.4km since its launch at Arden in May 2020.

Earlier this year, the machine bored a 1.2km tunnel between the western tunnel entrance in Kensington and Arden station. The TBM, one of four excavating the Metro Tunnel Project’s twin tubes across Melbourne, will now be moved through the Parkville station box, cleaned, recommissioned and relaunched to mine toward the new State Library station site in the CBD. Another TBM, Meg, working on the second tunnel tube, is expected to breakthrough into Parkville in the coming weeks.

The remaining two TBMs, Millie and Alice, are currently excavating a 1.7km tunnel towards the eastern tunnel entrance in South Yarra. They were both launched from Anzac station earlier this year. Geological conditions vary throughout the alignment from soft siltstones and mudstones to hard basalt.

The Metro Tunnel Project comprises twin nine-kilometre rail tunnels stretching from the west of the city to the south-east and will form part of a new Sunbury to Cranbourne/Pakenham line. The scheme includes five new underground stations at Arden, Parkville, State Library, Town Hall and Anzac to be constructed using a variety of techniques.

The station boxes at Arden, Parkville and Anzac will be built using diaphragm walls and top-down construction techniques; while roadheaders will be used for the station caverns and underground passenger walkways at State Library and Town Hall, located up to 30m below ground.

Of special interest at State Library and Town Hall stations will be the construction of ‘trinocular’ caverns. These will occur where three tunnels converge to form a large cavern which allows the integration of concourse and platforms on a single level.

The Metro Tunnel project is currently on track and is scheduled to be completed in 2025.