The technology involved in tunnelling projects today is simply stunning, and this was highlighted in Sydney earlier this week.

The tunnel-boring machine (TBM) sisters dubbed 'Maria' and 'Isabelle' are both hard at work on the Sydney Metro Northwest project. Churning through 100 cubic metres of rock per day, and operating 24 hours a day during the working week, these machines are testament to the technology available to civil engineering companies.

However, something of real note occurred earlier this week (August 25), Maria popped her head out from the underground at Cheltenham. Fortunately this event was planned with this location set to host a fresh air tunnel ventilation system and an emergency access point, set for use in 2019 once the train lines become live.

While progress is painfully slow, a time-lapse video showed the moment that Maria came to the surface and revealed the solid turning face used to carve the rock away. The visit to the surface was very brief with only three metres of Maria's cutter head exposed to the air. The TBM then continued to bore away underground with the gap now ready for further inspection from the project team.

Maria and Isabelle have made excellent progress across the Sydney Metro Northwest project thus far with two-thirds of the 30-kilometre tunnel completed. Maria alone has dug more than four kilometres along the system.

Bluey's role

As with many other product providers and support teams, Bluey is also putting in the hard yards on the Sydney Metro Northwest project.

Responsible for the waterproofing of the cross passages built between the two TBM tunnels, this task involves difficult and complex termination details. We've engineered these to ensure that up to 60m of water head can be resisted where the cross passage meets the TBM segmental lining – vital for underground projects of this nature.

Project background

The tunnelling section of the Sydney Metro Northwest project launched in September 2014. Maria and Isabelle and two other TBM are sharing responsibility of the two tunnels starting from different locations.

Tunnelling progress is steady with over 20 kilometres completed already. However, with a lowest point of 58 metres, there are more challenges ahead for the civil-engineering teams on site.

As Maria, Isabelle and the other TBM continue to make progress, we'll keep you updated with their outstanding efforts.

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