After completing tunnelling at Town Hall Station, each machine underwent a dismantling process that lasted several weeks, breaking the machine down to its components to return to surface level.
The backup gantries, including mechanical and electrical components, were transported back through the completed tunnels to Anzac and Arden stations, where they were dismantled and each component reassessed for reuse.
The cutter heads were too big to remove from the stations intact; so they were cut into pieces using an oxyacetylene torch, with the pieces sent away as scrap steel to be recycled.
Each TBM was equipped with a state-of-the-art navigation system to ensure accuracy in digging along the tunnel alignments.
The TBMs were 7.28 m in diameter, weighing more than 1,100 t and reaching 120 m in length.
Each machine on the project was staffed and monitored 24/7, and came fully equipped with staff facilities, including an office, kitchen and toilets.
A crew of 10 people worked on each TBM at any one time.
The Metro Tunnel Project used mix shield TBMS – commonly known as slurry TBMs – that are purpose-built to suit the local ground conditions.
Once the TBM’s cutterhead bores through the ground, the excavated material will be mixed with slurry and transported back to the above-ground slurry treatment plant.
The excavated material is then separated from the slurry and transported to a disposal site.
The Melbourne Metro Tunnel is expected to be completed by 2025.
For more information visit the Metro Tunnel website.