Joan starts tunnelling
Posted: 24 Sep 2019
We have reached a major milestone with tunnelling commencing on the North Melbourne to Kensington section of the Metro Tunnel Project.
The tunnel boring machine (TBM) Joan is the first to break ground, with Meg to follow shortly, while two others – Alice and Millie – will be launched in 2020 from the future Anzac Station in the Domain Precinct towards South Yarra.
During tunnelling, the TBMs will pipe the excavated soil (slurry) back to a site in North Melbourne, whilst also lining the tunnel with curved concrete segments.
Joan and Meg will arrive at Kensington in early 2020 before being transported back to site in North Melbourne where they will start excavating towards Parkville before tunnelling towards the CBD.
- At 120m long, the TBMs are as long as 3 E-Class trams end-to-end.
- 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.
- 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.
- 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!
- A crew of up to 10 people, including a TBM operator, will work on the TBM at any one time.
- 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.