The TBMs – named ‘Meg’, ‘Alice’, ‘Millie’ and ‘Joan’ – are being carefully dismantled before being transported back through the tunnels.
The machines are Herrenknecht Mixshields, running 120 m long and featuring cutterheads with diameters of 7.2 m.
The machines can bore through a variety of ground conditions, from hard rock to sand, and use slurry as an excavation medium, for both ground support and the transportation excavated spoil to the surface.
Each TBM is operated by a crew of approximately 10 people.
Their removal follows 20 months of digging over a length of 9 km, with Meg the last to arrive at the new Town Hall Station destination back in May.
The machines will be returned to the supplier and reassessed for potential reuse.
Digging continues on the project as roadheader machines excavate the tunnels next to the platforms at Town Hall Station.
Works are also continuing on the 26 cross passages located along the Metro Tunnel’s alignment.
The Metro Tunnel is due to be completed in 2025.
For more information visit the Metro Tunnel website.