All tunnelling has now been finished on the Sydney Metro City and Southwest project, following the arrival of tunnel boring machine (TBM) Kathleen at the north of Sydney Harbour.
TBM Kathleen has dug two 885 metre tunnels from Barangaroo to Blues Point under Sydney Harbour.
The machine has cut through around 175,000 tonnes of sandstone clay and marine sediments to build both harbour tunnels, which are bout 40 metres below sea level at the deepest point.
It took two months to build the second faster, one month faster than the first, as the team learned more about how to best operate the machine. The giant cutter head was modified, and the tunnelling process was changed to better deal with the clay material at the bottom of the harbour.
Five TBMs involved on the Sydney Metro project have delivered 31 kilometres of fully lined tunnels in 17 months.
TBM Kathleen and is named after Kathleen Butler, who played a pivotal role in the construction of the Sydney Harbour Bridge as the technical advisor to engineer John C Bradfield.