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Metro Tunnel

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.

The last piece of our first tunnel boring machine (TBM) arrived at the future North Melbourne Station site last month. The TBM pieces are now being stockpiled on site while excavation of the west station box is completed.

Posted by Metro Tunnel on Sunday, 17 March 2019

Introducing our TBM names


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 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 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 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

TBM map

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 Magnificent Machines


Big and beautiful

At 120m long, the TBMs are as long as 3 E-Class trams end-to-end. They weigh a whopping 1,100 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!


Up to 14 people work in each TBM at any one time. Workers in the TBM include the operator, 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