Tunnel boring machine (TBM) Kathleen has been launched 30 metres below ground to begin building a tunnel under Sydney Harbour for Sydney Metro.
The TBM has already tunnelled the first 100 metres of its one kilometre journey
When the first tunnel is completed, TBM Kathleen will then build a second tunnel under Sydney Harbour. It will then have its cutter head removed and main section lifted out at Blues point, where it will be placed on a barge and returned to Barangaroo while its support trailers are pulled back through the first tunnel.
It is expected to tunnel through clay, silt and sediment and will use tunnelling technology to safely make its way under the harbour. At its deepest point, it will be 40 metres below the harbour.
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Four TBMs have already completed more than half of the 31 kilometres of tunnel for Sydney Metro City and Southwest.
The TBM is named after Kathleen Butler, who played a vital role in the construction of the Sydney Harbour Bridge as the technical advisor to engineer John JJC Bradfield.
It is expected to take TBM Kathleen four months to complete its first tunnel.