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Metro Tunnel

Tunnel boring machines

A tunnel boring machine (TBM) is a machine that is used to excavate tunnels. TBMs can bore through a variety of ground conditions, from hard rock to sand.

Four TBMs are building the Metro Tunnel with more than 50% of tunnelling complete. Follow our progress on our TBM tracker.

Tunnelling progress overview

Arden to Parkville

In 2020, two tunnel boring machines (TBMs) were launched separately from the Arden Station site towards Parkville.

The first TBM, Joan, was launched from Arden in May 2020 and was followed by the second TBM, Meg, in early June.

In August 2020, TBM Joan broke through into the Parkville Station site. This completed the first of the twin tunnels from Arden to Parkville. TBM Meg broke through into the Parkville site in late September 2020.

Watch our Construction Manager Bored Tunnels – West, Adam Gorny, provide a general overview about tunnelling from Arden to Parkville.

Parkville to State Library

After reaching the Parkville Station site, TBMs Joan and Meg were transferred across the station box and prepared for relaunch.

TBM Joan began the one-kilometre journey towards the State Library Station site in October 2020, followed by TBM Meg in November.

TBM Joan broke through at the State Library Station site in December 2020 and relaunched in February to tunnel towards the Town Hall Station site.

TBM Meg broke through at the State Library Station site in February 2021 and will be relaunched shortly to dig the parallel tunnel.

Domain to South Yarra

In April and May 2020, two TBMs were launched separately from the Anzac Station site towards the eastern tunnel entrance at South Yarra.

TBM Millie broke through at South Yarra in September 2020, and TBM Alice arrived in October.

Watch our Construction Manager Bored Tunnels – East, Andreas Mindt, provide a general overview about tunnelling from Domain to South Yarra.

Domain to Town Hall

After being transported back to the Anzac Station site, in December 2020 TBM Millie has been relaunched towards the CBD. In January 2021, TBM Alice was also relaunched towards Town Hall Station.

Tunnelling in the CBD

In 2021, following roadheader excavation of the tunnels through the CBD stations, TBMs will carve out the twin tunnels between Town Hall Station and State Library Station, around 30-40 metres below Swanston Street.

Explaining the tunnelling process

In August 2019, as Joan the TBM prepared to launch towards Kensington, our Director of Tunnels and Underground Stations explained how tunnelling operations would take place on the Metro Tunnel Project.

Environmental management

The Metro Tunnel Project has a comprehensive environmental management system in place for the construction and operation of the new twin tunnels.

Watch our Environment Manager, James Hamilton, provide an overview about environmental management, including noise and vibration, during tunnelling.