Tunnel Boring Machines
Four giant Tunnel Boring Machines (TBMs) are needed to dig the Metro Tunnel.
Lowered into the ground at North Melbourne and St Kilda Road in pieces and then assembled, they operate as moving factories travelling deep under Melbourne.
TBMs perform two main tasks:
- Excavating rock and soil with a rotating cutter head at the front of the machine before it is transported via pipes running through and behind the TBM.
- Progressively installing curved concrete segments to create a watertight lining inside the tunnels.
Track their journey
Our first TBM has arrived in Melbourne and our second is on its way, track their journeys here.
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.
Digging the Metro Tunnel
Which way to the surface?
Step 1
The TBMs will be launched at North Melbourne and Anzac station sites.
Step 2
They will head away from the CBD on the first leg of their journey.
Step 3
The TBMs are then retrieved in Kensington and South Yarra.
Step 4
They are dismantled and trucked back to their starting points.
Step 5
Finally, the TBMs are relaunched towards the CBD for the last leg of their journeys.
The Magnificient Machines
Big and beautiful
At 100m long, the TBMs are as long as 3 E-Class trams end-to-end. They weigh a whopping 1,000 tonnes, equal to the weight of around 150 elephants.
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 7.2m in diameter and each of the cutterhead’s front discs weigh 200kg.
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
Up to 14 people work in each TBM at any one time. Workers in the TBM include the pilot, who drives the TBM, as well as tunnel and electrical engineers.
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.
Learn more at Metro Tunnel HQ
A scale model is on display these school holidays at Metro Tunnel HQ on Swanston Street.