Elizabeth's massive cutter head has been lowered into the Bella Vista tunnelling construction site and attached to the rest of the 120 metre-long tunnel boring machine (TBM). This is an important sign that tunnelling is getting closer.
It took two 500 tonne cranes about seven hours to lift the 105 tonne circular cutter-head into place. The cutter-head is made up of 40 tungsten steel cutters, which will split the rock as Elizabeth moves forward, digging about 120 metres a week.Each cutter weighs 250 kilogram and will be replaced approximately every three weeks, as they wear down. The cutter-head is now in place at the front of Elizabeth and all of the pieces are now at Bella Vista.
Over the past three weeks, 22 large pieces of Elizabeth have been lifted into position ready for final assembly and commissioning. While the machine looks relatively complete, a crew of 71 workers are now bolting, welding and fastening thousands of smaller components into place ready for tunnelling. To get down to tunnelling depth at Bella Vista, about 120,000 tonnes of rock was removed from the Bella Vista station box, and most of it re-used on the wider construction site.
Elizabeth is being connected to tunnelling support services above ground including power, ventilation, compressed air, grout plant, hydraulic cooling towers, water pumps, a water treatment plant and spoil conveyors.
The four TBMs have been specially designed for the geology in Sydney and will mostly dig through Sydney sandstone and shale.