TBM Grace has officially reached the halfway point of her tunnelling journey from Forrestfield to Bayswater! The major milestone was reached on 21 November as she tunnelled over the 3751m mark, with 2130 tunnel segment rings installed.
Since setting off from Airport Central Station in June, TBM Grace has successfully tunnelled her way underneath the airport, clearing the runways and is now approaching the Airport West Emergency Egress Shaft. Once she arrives, she’ll take a short break to undergo a ‘hyperbaric intervention’ – a health check on the wear and tear of the cutting tools of the TBM, that can be replaced as required.
As the tunnelling takes place more than 20m underground, the atmospheric pressure is higher than at ground level and so to be able to replace parts of the cutter head, workers need to spend time in a decompression chamber to adjust to the hyperbaric conditions. It’s like diving, but without water.
As always, trailing at a safe 400m distance behind TBM Grace is TBM Sandy, due to reach her halfway point of tunnelling this month.
To find out more about the Forrestfield Airport Link see the project page and sign up for updates.