The construction of the 24-kilometre twin metro railway tunnels for Sydney Metro West has reached a key milestone, with two tunnel boring machines (TBMs) breaking through solid rock walls to arrive at the junction caverns 24 metres below Clyde. This achievement marks the completion of more than 80 per cent of the project’s tunnelling.
TBM Dorothy reached the junction caverns in February after a three-month journey excavating 1.1 kilometres from Clyde. TBM Betty, which is slightly ahead in progress, arrived in December 2024 after tunnelling a parallel route. After spending seven weeks traversing the cavern and undergoing scheduled maintenance, TBM Betty has resumed tunnelling towards Parramatta.
The junction caverns play a crucial role in the metro network, featuring service tunnels that connect to the above-ground stabling and maintenance facility, where trains will be housed when not in operation.
Since beginning their westward tunnelling in September 2024, TBMs Betty and Dorothy have been operating continuously, excavating approximately 200 metres of tunnel per week. To date, they have completed 5.7 kilometres of twin tunnels between Sydney Olympic Park and Clyde, removing over 1.1 million tonnes of material—equivalent to approximately 180 Olympic-size swimming pools.
During excavation, more than 41,000 precast concrete segments have been installed to form the tunnel walls. Each segment weighs approximately 3.8 tonnes, with six segments required to complete a full tunnel ring.
The TBMs will now construct an additional 1.1-kilometre section, reaching the future Parramatta Metro Station by mid-year.
Sydney Metro West tunnelling
Tunnelling for Sydney Metro West has been ongoing since April 2023, with progress across multiple sections:
- TBMs Betty and Dorothy have completed over 75 per cent of the nine-kilometre tunnel stretch between Sydney Olympic Park and Westmead.
- TBMs Daphne and Beatrice completed the 11-kilometre twin tunnels between The Bays and Sydney Olympic Park in October 2024.
- TBMs Jessie and Ruby have finished 33 per cent of the 2.3-kilometre tunnels between The Bays and Hunter Street in the Sydney CBD, with the remaining 1.7 kilometres being excavated by roadheader machines.
Following tunnelling tradition, TBMs Betty and Dorothy have been named after notable women. TBM Betty honours Olympic champion and former Parramatta resident Betty Cuthbert, while TBM Dorothy is named after human rights activist Dorothy Buckland-Fuller.
Sydney Metro West remains on track for completion, with services expected to commence in 2032.
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