File:Sydney Metro mega borers before and after

Description
Before and after: this is what the immense forces of tunnelling under Sydney Harbour do to a nice, new, clean, white mega borer.

Sydney Metro’s 975-tonne specialised tunnel boring machine Kathleen dug through more than 87,000 tonnes of sandstone, clay and marine sediments for the first of two metro railway tunnels deep under the Harbour.

Take a look at what happened to her 90-tonne cutter head after this historic four-month dig, and compare it with before.

She’s was then reassembled to deliver the second tunnel from Barangaroo to Blues Point.

First published: February 2020