The historic first rail crossing deep under Sydney Harbour is underway after Herrenknecht Mixshield TBM Kathleen launched 30m below ground from Barangaroo.
TBM Kathleen has already tunnelled the first 100m of its one kilometre journey underneath the Harbour.
Once the first tunnel is complete, Kathleen will then build the second tunnel under Sydney Harbour before being retrieved at Blues Point and taken away by barge.
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The machine is expected to tunnel through clay, silt and sediment under the harbour.
Four other Herrenknecht double-shield, hard-rockTBMs have already completed over half of the 31km of 6m i.d. tunnel for Sydney Metro City & Southwest.
This specialised TBM is named after Kathleen Butler, who played a vital role in the construction of the Sydney Harbour Bridge as the technical advisor to legendary engineer John JJC Bradfield.
It is expected to take the TBM about four months to complete the first tunnel.
Together, all five TBMs will deliver twin 15.5km rail tunnels for Australia’s biggest public transport project.
Tunnelling contractor, John Holland/CPB/Ghella was awarded the $2.81bn contract in June 2017. The current schedule sees the tunnelling contract conclude in 2021.