Building the Metro Tunnel

Tunnelling update

TBM Joan has travelled more than 250 metres toward Kensington and has installed more than 140 rings to line the tunnel.

TBM Meg has travelled more than 50 metres toward Kensington and has installed more than 20 rings to line the tunnel.

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Tunnel staging, alignment and depth maps
Introducing our TBM names
Digging the Metro Tunnel
Magnificent machines: TBM facts
TBM gallery
Learn more

Tunnel staging, alignment and depth maps

In mid-2019, two tunnel boring machines (TBMs) were assembled at the new North Melbourne Station site.

The TBMs have now been launched separately, and are tunnelling towards the western tunnel entrance at Kensington.

The TBMs will arrive at Kensington and will be transported back to site in North Melbourne to be reassembled in early 2020.

The TBMs have been launched separately at North Melbourne and commenced tunnelling towards Parkville before they will eventually tunnel towards the CBD.

At the future Anzac Station in the Domain Precinct, two TBMs will be assembled in the station box and will be launched separately in 2020 to tunnel towards the new tunnel entrance at South Yarra.

The TBMs will arrive at South Yarra and will be transported back to site in Domain.

The TBMs will be reassembled in the station box and will start their journey towards the CBD, and under the Yarra River.

Station Depths

TBM map

Explaining the tunnelling process

Introducing our TBM names

Joan

Joan Kirner was the first female Premier of Victoria (serving from 1990 to 1992) as a member of the Labor Party. She was MP for Williamstown, and while Education Minister her reforms included pioneering the Victorian Certificate of Education (VCE).

Meg

Meg Lanning captains the Australian women’s national team and the Victorian Spirit. She holds the record for the most centuries in women’s one-day internationals and was the youngest Australian (male or female) to score an international 100, when she was 18.

Alice

Alice Appleford was an Australian civilian and military nurse who took part in both World Wars. During the First World War she served in hospitals in Egypt and France and was one of only seven Australian nurses decorated with the Military Medal for Gallantry.

Millie

Millie Peacock was married to three-time Premier of Victoria Sir Alexander Peacock. After his death in 1933, she won the by-election to succeed him and became the first woman elected to the Parliament of Victoria.

What type of TBMs will be used for the Metro Tunnel?

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.

The Metro Tunnel Project will use mix shield TBMs – commonly known as slurry TBMs – that are purpose-built to suit the local ground conditions along the tunnel alignment. Once the TBM's cutterhead bores through the ground, the excavated material will be mixed with slurry and transported back to the above ground slurry treatment plant.

The excavated material is then separated from the slurry and transported to a disposal site.

To construct the tunnels, the TBMs will progressively line each tunnel with curved concrete segments. The twin tunnels will comprise 56,000 individual concrete segments.

Each TBM is equipped with a state-of-the-art navigation system that will ensure accurate tunnel alignments are achieved.

What is the geology like?

The geology of the area is variable. The TBMs will be required to excavate through soft soils such as Coode Island Silt, and hard basalts under the Yarra River and in some sections of the western alignment. Many sections of the tunnel alignment feature a ‘mixed-face’ geology, which is both parts hard and soft.

How big are the TBMs?

Each TBM is 7.28 metres in diameter, 120 metres long and weighs more than 1,100 tonnes. The heaviest component is the cutterhead, which weighs 100 tonnes.

How fast do the TBMs travel?

On average the TBMs will move around 10 metres every 24 hours.

How many people will be operating each TBM?

A crew of up to 10 people, including a TBM operator, will work on the TBM at any one time.

Managing noise and vibration during tunnelling

Managing noise and vibration during tunnelling will be based on a best practice approach as undertaken by Metro Tunnel’s contractors on similar projects around the world.

Prior to tunnelling, comprehensive geological testing and environmental assessments are completed.

Property condition surveys will be offered to properties based on an environmental assessment.

Properties located near the path of the TBMs may experience low levels of noise or vibration, however individuals experience noise and vibration differently. During tunnelling, noise, vibration and ground movement will be managed in line with strict Environmental Performance Requirements.

Properties located near the path of the TBMs will be contacted with further information prior to tunnelling commencing in their area.

The magnificent machines

Not so boring

At 120m long, the TBMs are as long as 3 E-Class trams end-to-end.

Silver lining

The TBM not only digs the tunnels but it also seals them. Concrete segments are delivered to the TBM and installed to line the tunnel walls. A total of 56,000 individual segments will be used to build the Metro Tunnel.

Making headway

At the front of the TBM is the ‘cutterhead’, which acts as a drill that can tunnel through rock six times harder than concrete. The face of the cutterhead is 7.28m in diameter.

Rock and roll

TBMs bore through a variety of ground conditions, from hard rock to sand, travelling around 10m a day. The amount of excavated material removed would fill the MCG 1.2 times!

Heave-ho

A crew of up to 10 people, including a TBM operator, will work on the TBM at any one time.

Home sweet home

Each TBM is manned and monitored 24 hours a day, 7 days a week. It is fully equipped with facilities for staff, including an office, kitchen and toilets.