Major tunnelling works complete as all four TBMs reach final stop
Posted: 24 May 2021
All four tunnel boring machines (TBMs) digging the Metro Tunnel’s 6.3 metre-high, twin 9km tunnels have now completed their works after 20 months.
The last TBM to hit the finish line was Meg, which arrived at the new Town Hall Station last week. The other TBMs – Millie, Alice and Joan – arrived at the site over the past month.
Between them, the TBMs have lined the tunnels from South Yarra to Kensington with around 250,000 tonnes of concrete, tunnelling an average of 90 metres per week. They dug as deep as 40 metres below ground, passing 12 metres under the Yarra River, seven metres beneath the Burnley tunnel and just 1.5 metres below the City Loop.
The huge TBMs are now being dismantled. The ‘skin’ of each will remain underground to form part of the permanent tunnel lining, and the remaining TBM components will be assessed for potential reuse on other tunnelling projects.
There is much more work to be done before the Metro Tunnel is completed in 2025 – including more digging works using roadheaders to complete the final section of tunnels alongside the platforms at Town Hall Station. Work is also continuing on building the five new underground stations.