Four tunnel boring machines (TBM) are now leaving Sydney after completing tunnelling under the city, delivering 30 kilometres of twin metro railway tunnels.
The TBM cutterheads, each weighing 100 tonnes are now being lifted out of construction sites in four military style operations.
This marks the successful completion of major tunnelling construction under the city centre and the city’s north on the Sydney Metro City and Southwest project.
Each TBM tunnelled through sandstone and shale under Sydney at an average pace of 167 metres per week.
Cutters on the TBMs had to be changed about every 10 days because of the forces of tunnelling, each machine went through about 200 cutters in total.
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TBMs named Nancy and Mum Shirl each built 8.1 kilometre tunnels from Marrickville to Barangaroo, passing through new metro stations at Waterloo, Pitt Street and Martin Place.
They started tunnelling in October and November 2018 respectively, and they each arrived at Barangaroo in December 2019 and January 2020.
Two other TBMs, Wendy and Mabel each built 6.1 kilometre tunnels from Chatswood to Blues Point passing through new metro stations at Crows Nest and Victoria Cross.
Wendy and Mabel started tunnelling in January and February 2019 and arrived at Blues point in November and December 2019.
A 330-tonne tower crane extracted TBMs Nancy and Mum Shirl from Barangaroo as they were disassembled and returned to the manufacturer.
There is still one remaining TBM on the project, Kathleen, which is currently completing the second metro railway tunnel under the Sydney harbour.