Catherine and Elizabeth will join Mary this week as all three tunnel boring machines (TBMs) roar into action for the first time on the $15.4 billion River Torrens to Darlington (T2D) Project.
The two huge machines – named after pioneering South Australian women – are in the final stages of preparations and are expected to start excavating in the coming days, joining Mary which has already carved around 100m beneath South Road.
This marks the first time in Australian history that three large-scale TBMs are tunnelling simultaneously on the same underground road project.
As the mega machines make their way beneath South Road the millions of tonnes of excavated material will need to make its own journey to the surface.
Together, the trio will excavate around 5 million tonnes of rock and soil, known as spoil, as they construct the northern and southern tunnels.
Spoil will travel from the TBMs by conveyor to a shed before being loaded into covered trucks, then transported to the re-use site at Gillman.
Around 7.5 million tonnes of spoil is expected to be generated across the whole T2D project, including approximately 5 million tonnes from tunnelling and a further 2.5 million tonnes from civil works.
Each stretching around 100m in length and weighing 3500 tonnes, the TBMs are the largest pieces of construction equipment ever used in South Australia.
TBM Mary was first to begin her journey beneath South Road from the project's Southern Precinct at Clovelly Park, with Catherine now preparing to join her on the 4.5km journey towards Glandore to construct the twin southern tunnels.
Further north, TBM Elizabeth is preparing to start her journey from the project's Central North Precinct at Hilton, excavating the first of the 2.2km northern tunnels toward the Brickworks Marketplace at Torrensville.
Once there, Elizabeth will be turned around and reassembled for the southbound return journey to Hilton.
The use of three large-scale TBMs allows both the northern and southern tunnels to be constructed 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 road within the tunnels, installing safety, mechanical and electrical systems, testing and commissioning, and completing compliance checks.
The open motorway section, including bridges and footpaths, will also need to be completed and connected to the tunnels.
The T2D Project is the final 10.5km section of the North-South Corridor, and will complete 78km of non-stop, traffic light-free motorway between Gawler and Old Noarlunga.
