Metro Tunnel TBM dismantling underway

29 July 2021

Following the completion of tunnelling in May 2021, the four slurry TBMs which since April 2020 have been excavating Melbourne’s Metro Tunnel are now being retrieved from underground.

Dismantling is taking place of the 7.28m-diameter cutterheads, breaking them into smaller pieces to allow conveyance through the tunnel and returned to the suppler for reuse evaluation.

The four machines have mined at depths ranging between 12 – 40m at a typical daily advance rate of 10m every 24hrs. They have faced a variable geology comprising soft soils, such as Coode Island Silt, as well as hard basalts under the Yarra River and in some sections of the western alignment. Along many sections of their drives, ‘mixed-face’ geologies of hard and soft soils were encountered.

Despite the dismantling of the TBMs, excavation is still continuing on the project by roadheaders mining the tunnels next to the platforms at Town Hall Station. Work is also continuing on 26 cross passages.

The Metro Tunnel project will be a metro-style, end-to-end rail line across Melbourne, with twin 9km tunnels and five new underground stations. It will stretch from Sunbury in the west to Cranbourne/Pakenham in the south-east. The project is on-track for completion by 2025.