After months spent assembling one of the largest machines ever used in South Australia, tunnelling is now underway on the $15.4 billion River Torrens to Darlington (T2D) project to deliver a non-stop South Road.
Tunnel boring machine (TBM) Mary has started excavating the first 4.5-kilometre Southern Tunnel from the Southern Precinct at Clovelly Park to Glandore.
Operating 24/7, Mary will progress about eight to 10 metres per day, with up to 20 specialised workers inside at any one time as she embarks on the state’s first major underground road tunnelling project.
Mary’s first components arrived in Adelaide in October 2025. Since then, each component has been lifted into the launch box by a 500-tonne gantry crane before being assembled into the mega machine.
Measuring about 100 metres in length, 15 metres in diameter and weighing 3,500 tonnes, Mary is one of three large-scale TBMs being used on the T2D project.
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“This is a momentous occasion for the largest ever infrastructure project in our state’s history,” said SA Premier Peter Malinauskas. “After all the careful planning and machinery assembling, tunnelling is now underway to deliver South Australia a non-stop South Road.”
The project’s second TBM, Catherine, will soon launch from the Southern Precinct to excavate the second parallel 4.5-kilometre Southern Tunnel.
Further north, the third TBM, Elizabeth, will launch from the project’s Central North Precinct at Hilton to construct the 2.2-kilometre Northern Tunnels.
Named after suffragists Mary Lee, Catherine Helen Spence and Elizabeth Webb Nicholls, the project’s three TBMs recognise the trailblazers who helped shape South Australia.
The use of three TBMs allows both the Northern and Southern Tunnels to be constructed concurrently, helping deliver a non-stop South Road by 2031.
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.
“Every day, thousands of South Australians have driven past the cranes, sheds and construction work reshaping South Road,” said SA Minister for Infrastructure and Transport Joe Szakacs. “Now, attention turns underground as the next chapter of the project begins, with tunnelling commencing on the non-stop South Road.”
The Australian and SA governments have each committed $7.7 billion towards the project.
With tunnelling now underway, the community can follow Mary’s journey using the new online TBM Tracker. The tracker will provide regular updates on each TBM’s approximate location and other key information, with updates on Catherine and Elizabeth available once they begin tunnelling.
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