The first of two tunnel boring machines (TBM) has commenced its final journey beneath Sydney Harbour in a major milestone for large scale project coordinator ACCIONA.
Built to handle some of the most complex geological conditions, these mega boring machines are equipped with state-of-the-art technology to deliver a significant piece of infrastructure for Sydney: the Western Harbour Tunnel.
TBM Patyegarang and sister TBM Barangaroo are the largest tunnel boring machines in the southern hemisphere, with Patyegarang this week having begun carving her way beneath Sydney Harbour.
From 44.7m below Birchgrove Oval, Patyegarang began her steady march towards Waverton late on Friday 12 June after final testing wrapped up. It marks the start of the final stage of excavation for the project.
Each one of the TBMs measures 15.7m wide and weighs about 4,350 tonnes — making them the largest TBMs ever assembled underground.
As they move forward, they will line the tunnel with around 13,000 precast concrete segments, building the tunnel structure as they go.
The TBMs are supported by an underground slurry treatment plant that pumps up to three million litres an hour to each TBM, keeping tunnelling stable. The plant then filters and sends the slurry mix back to the TBMs, while the solid rock material separated from the slurry is recycled for other projects.
Built entirely underground to limit local disruption, the slurry treatment plant stretches over 100m long and is up to 15m tall — making it one of the largest plants ever to be assembled and operated underground.
Barangaroo, named alongside Patyegarang in honour of notable Aboriginal women, is not far behind, with assembly 94 per cent complete.
She is expected to begin tunnelling in about four weeks.
Together, the two machines will excavate the final 1.5km of twin motorway tunnels beneath the harbour, reaching depths of up to 50m below sea level.
They will run around the clock, with about 40 people working on them at any one time.
“This is a major milestone for the Western Harbour Tunnel project, marking the beginning of the final stage of excavation under Sydney Harbour,” said NSW Minister for Roads Jenny Aitchison on a recent visit to inspect the final stages of TBM testing.
“Assembling these mega machines entirely underground has been incredibly complex work, and the team is doing a fantastic job.
“Building and operating the tunnel boring machine’s slurry treatment plant underground is not only a major win for the local community, but a significant engineering first for Australia and the world.”
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