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Major Sydney tunnelling completed

Four tunnel boring machines (TBM) have completed tunnelling under the city, delivering 30 km of twin metro railway tunnels.

This marks the completion of major tunnelling construction under the centre and north of Sydney for the Sydney Metro City project.

The 1,100 t TBMs each tunnelled through sandstone and shale at an average rate of 167 m per week.

The machine’s 38 cutters, which were made from hardened steel and weighed 250 kg, had to be changed every ten days due to tunnelling forces, with a total of approximately 200 cutters used on each TBM.

TBM Nancy and Mum Shirl each built 8.1 km tunnels from Marrickville to Barangaroo while TBMs Wendy and Mabel each built 6.1 km tunnels from Chatswood to Blues Point.

Now, the TBM’s 100 t cutterheads are being lifted out of their construction sites in four military-style operations.

Another TBM for the project is currently tunnelling under the Sydney Harbour to complete the second metro railway tunnel under the harbour.

For more information visit the Sydney Metro.

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