In one of Perth’s Forrestfield-Airport Link’s biggest milestones to date, Herrenknecht Variable Density TBM Grace broke through into the underground station box at Airport Central Station on the evening of Tuesday May 8, 2018.
It’s the first time the TBM has ‘surfaced’ since the Salini-Impregilo (SI-NRW) JV began tunnelling at Forrestfield nine months ago, having travelled 1.9km and installed 1188 rings.
TBM Grace entered the Airport Central Station box via a mass concrete false block, used to stabilise the walls and reduce water ingress. Grace was guided through the 12.5m block over a period of 24 hours, with a team of 15 present inside the machine for the final breakthrough. She will continue to advance into the station box in coming weeks whilst undergoing maintenance.
The project’s second TBM, Sandy, is due to arrive at Airport Central Station later this month and will follow the same process as Grace. TBM Sandy has so far travelled 1.8km and installed 1121 rings.
A significant milestone has also been reached at Bayswater Junction with the completion of all 133 diaphragm wall (d-wall) panels for the tunnel portal and dive structure. The final d-wall was poured in the first week of May and marks the completion of d-wall construction across the entire project. Attention will now turn to excavation of the 400m-long dive structure and tunnel portal, where trains will enter and exit the Forrestfield Line tunnels.
Excavation within the Redcliffe Station box is now expected to be completed within the coming week. More than 42,000m3 (97 per cent) of spoil has been removed to date.
With Redcliffe Station the next stop for the TBMs on their 8km journey to Bayswater, works will turn to the pouring of concrete for the base slab of the underground station box. Construction of the base slab is expected to begin imminently and will continue until late August. After completion, dewatering at the site will be turned off.
The $1.86bn Forrestfield-Airport Link is jointly funded by the Australian and Western Australian governments and will deliver a new rail service to the eastern suburbs of Perth – with the three new stations at Redcliffe, Airport Central and Forrestfield via the 8km long twin tunnels.
In April 2016 the PTA awarded the $1.176bn single-package, lump sum design, construct and maintenance contract to the Salini Impregilo – NRW Joint Venture.
TBM Grace began tunnelling in July 2017, with TBM Sandy following in September. Their underground journey is scheduled to take almost two years with breakthroughs slated for April 2019 and June 2019 respectively.