Identical boring machines to operate continuously for two years to construct Torrens to Darlington southern tunnels

South Australia gets its first look at a pair of massive tunnel boring machines, each as big as a warehouse, which will operate around the clock to dig the Torrens to Darlington parallel tunnels.

A pair of massive tunnel boring machines, each the size of a large warehouse, will operate around the clock for two years to construct the Torrens to Darlingtonparallel southern tunnels.

New details have been revealed about the identical machines, each expected to cost about $180m, which will begin boring at Clovelly Park and tunnel 4.5km north to Glandore near the Anzac Highway intersection.

North-South Corridor executive director Susana Fueyo said the operation will be a feat of engineering unlike anything the state has seen before.

A continuously-rotating “cutter head” will excavate the ground, with soil placed on a conveyor belt and taken up to the surface.

At the same time, the machine will also lay 15m concrete panels that are interlocked to form the sides of the tunnel.

“Everything is happening at once,” Ms Fueyo said.

“It’s like a continuous factory under the ground.”

The machines are as big as a warehouse and at their deepest points, the top of the tunnels will be 40m underground. They will each be three lanes wide.

Four million cubic metres of clay-rich soil will be removed and collected in a purpose-built shed at the southern laydown area, which must be approved by the EPA for acoustics, dust and air quality.

The soil will be analysed and taken to disposal sites, which Ms Fueyo said are still being investigated.

“We try to seek out sites that need development, so you can place (the soil) and it allows for development to happen,” she said.

A purpose-built substation will be built at the same end to power the machines, which will be used to power the tunnel system at the conclusion of construction.

A replica of the tunnel boring machines used in the Sydney Metro project is currently on loan in Adelaide from the Victorian Tunnelling Centre.

The machines that will be used on the Torrens to Darlington project will look very similar, but more geo-testing is required before the design of the cutter head is finalised.

The tunnel boring machines used on the Torrens to Darlington project will look similar to those used on the Sydney Metro project. Picture: Supplied

The machines, manufactured overseas but assembled at the site, will create about 160 jobs including operators and electricians, as well as workers who will make the concrete panels.

Transport Minister Corey Wingard said the project would elevate local engineering capability.

“It’s engineering that this state hasn’t seen before; it happens all over the world and we’re bringing this to Adelaide, South Australia,” he said.

The machines will be retrieved at the Glandore end but it is yet to be determined whether they will be used for the northern tunnels, which will stretch from Richmond to Brickworks.

Site works at Clovelly Park will begin in 2023, before the machines start in 2025.