Sydney Metro West tunnels enter final stretch after big breakthrough

04 Mar 2025 | Rail Express

The tunnel boring machines, which are nicknamed “TBM Dorothy” and ‘TBM Betty”, have broken through the solid rock walls at the Clyde Metro junction caverns. Image: Transport for NSW

Two tunnel boring machines (TBMs) constructing the huge Sydney Metro West tunnels have made a smashing entrance 24 metres below the surface at the Clyde Metro junction caverns.

This latest milestone means that over 80 per cent of the 24-kilometre twin metro railway tunnels have been completed.

The TBMs, which are nicknamed “TBM Dorothy” and ‘TBM Betty”, started tunnelling westward in September 2024.

Since then, they have been working around the clock to excavate about 200 metres of tunnel each week.

TBM Dorothy broke through the solid rock walls at the Clyde Metro junction caverns last month, after spending three months tunnelling 1.1 kilometres from Clyde.

TBM Betty has been tracking ahead, arriving at the caverns in December last year. TBM Betty spent seven weeks traversing the caverns and is now tunnelling towards Parramatta.

This junction cavern at Clyde will play a critical role in the Sydney Metro network as it connects the metro tunnels with the above ground stabling and maintenance facility, where the network’s new fleet of trains will be housed when not in service.

The tunnel boring machines have carved out 5.7-kilometres of twin tunnels between Sydney Olympic Park and Clyde so far. Image: Transport for NSW

So far, TBM Betty and TBM Dorothy have carved out 5.7-kilometres of twin tunnels between Sydney Olympic Park and Clyde, removing more than 1.1 million tonnes of material, equivalent to about 180 Olympic-size swimming pools.

Along the way, the TBMs have installed more than 41,000 precast concrete segments to line the new tunnel walls. Each precast segment weighs about 3.8 tonnes, with six segments pieced together to form one ring around the tunnel.

Both TBMs will now build a further 1.1-kilometre section of tunnels to reach the site of the future Parramatta Metro Station by mid-year.

This project will double rail capacity between the Sydney CBD and Parramatta CBD, and the Minns Labor Government has modified planning controls around a number of these new stations to speed up the delivery of new housing.

Minister for Transport John Graham said: “Like their standout namesakes, these huge tunnelling machines are breaking new ground, which will have a lasting impact and transform the way Sydney’s west moves for generations to come.

“The TBMs are headed for Parramatta, Sydney’s second biggest business district, as they continue to carve out this game-changing new railway line that is expected to move 30,000 passengers every hour during the morning peak when it opens in 2032.”

Premier of New South Wales Chris Minns said the tunnel breakthrough at Clyde is “another huge step forward” in the project.

“I want to thank the thousands of workers who have gotten this project to this point and will be working around the clock until Australia’s largest public transport project is opened.”