Another CBD breakthrough for Sydney Metro’s mega borers


A second mega boring machine has arrived deep under the Sydney CBD at the new Pitt Street metro railway station. 

Tunnel Boring Machine (TBM) Mum Shirl started digging from Marrickville on 5 November 2018 and has since carved through about 600,000 tonnes of rock – enough to fill 92 swimming pools – building about six kilometres of tunnel.

Mum Shirl installed 3,390 concrete rings to form the tunnel from Marrickville to Pitt Street.

Mum Shirl is one of five TBMs building the 15.5 kilometre twin railway tunnels between Chatswood and Sydenham.

Two TBMs are working on 8.1 kilometres of twin metro tunnels from Marrickville to the new Sydney Metro station sites at Waterloo, Central, Pitt Street, Martin Place and on to Barangaroo, where they will be removed from deep underground.

TBM Mum Shirl will spend about two weeks at Pitt Street undergoing planned maintenance before being re-launched through the opposite end of the station box towards Martin Place Station.

TBM Nancy arrived at Pitt Street two weeks ago, and is getting ready start the job of tunnelling towards Martin Place Station.

At Pitt Street Station, it has taken tunnel builders John Holland CPB Ghella nine months to remove about 92,000 tonnes of sandstone to build the underground station cavern in preparation for the two TBM’s arrival.

Machines which work underground on major tunnelling projects around the world are traditionally given female names.

Mum Shirl was an Aboriginal woman who dedicated her life to her community, raising 60 foster children.

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