Three tunnelling titans are now hard at work beneath Adelaide, with all the Albanese and Malinauskas Labor governments' $15.4 billion River Torrens to Darlington (T2D) project's large-scale Tunnel Boring Machines (TBMs) excavating their way towards a non-stop South Road.
For the first time in Australian history, three TBMs are now tunnelling simultaneously on the same underground road project.
Assembling and launching the 3,500-tonne mega machines is only the beginning, with an intricate operation also required to keep the largest pieces of construction equipment ever used in South Australia moving.
At the front of each TBM, is a 15-metre-high, 300-tonne cutterhead - fitted with 82 cutting discs weighing up to 350 kilograms each and almost 200 teeth - tasked with carving the path ahead on South Australia's largest-ever infrastructure project.
Different teeth and discs are used to tackle ground conditions as crews constantly monitor the mega machines, adjusting everything from cutterhead rotation speed, penetration rate and thrust force to keep tunnelling on track.
While the TBMs are expected to excavate approximately eight to 10 metres a day once fully up and running, the initial phase involves a more gradual ramp-up as crews closely monitor performance and fine-tune the machinery as it moves forward.
Despite weighing thousands of tonnes, keeping the TBMs moving requires close attention to every detail, right down to the individual cutting tools on their 300-tonne cutterheads.
The teeth and discs are regularly inspected for wear by specially trained workers, who undergo specialist hyperbaric training to safely enter a pressurised environment behind the cutterhead.
As the cutterheads carve the path ahead and Mary, Catherine and Elizabeth move forward, millions of tonnes of rock and soil, known as spoil, makes its way in the opposite direction.
Spoil travels from the TBMs by conveyor to the spoil shed before being loaded into covered trucks and transported to the re-use site at Gillman.
Around 7.5 million tonnes of spoil is expected to be generated across the T2D project, including approximately five million tonnes from tunnelling and a further 2.5 million tonnes from civil works.
The use of three large-scale TBMs allows both the northern and southern tunnels to be built concurrently, helping deliver a non-stop South Road by 2031.
Tunnelling across the project will take up to 24 months, with significant work to continue after the TBMs finish their journeys. This includes building the roads within the tunnels, installing safety, mechanical and electrical systems, testing and commissioning, and completing compliance checks.
The T2D project is the final 10.5-kilometre section of the North-South Corridor, and will complete 78 kilometres of non-stop, traffic light-free motorway between Gawler and Old Noarlunga.
The $15.4 billion project is jointly funded by the Albanese and Malinauskas Labor governments, with each committing $7.7 billion.
Quotes attributable to the Minister for Infrastructure, Transport, Regional Development and Local Government, Catherine King:
"The T2D project has achieved another important milestone, bringing us a step closer to completing the final piece of Adelaide's North-South Corridor.
"The Australian Government is proud to partner with the South Australian Government to improve safety, connectivity and productivity from Gawler to Old Noarlunga."
Quotes attributable to the South Australian Minister for Infrastructure and Transport, Joe Szakacs:
"For the first time in Australian history, three large-scale TBMs are tunnelling at the same time on an underground road project, and it's happening right here in South Australia.
"Mary, Catherine and Elizabeth will now work in concert underneath Adelaide to deliver a non-stop South Road.
"We remain steadfast in our commitment to delivering South Australia's largest ever infrastructure project on time and on budget."
Quotes attributable to Federal Member for Boothby Louise Miller-Frost:
"Every week brings fresh progress on the T2D project, which continues to charge ahead in earnest.
"This massive project is supporting 5,500 jobs each year, creating a skills legacy for South Australia."
