Isabelle joins the big dig


Tunnel boring machine (TBM) 3 Isabelle is the first tunnel boring machine to start digging from the Cherrybrook construction site. She joins TBM1 Elizabeth and TBM2 Florence in building Australia's longest railway tunnels and will travel 6 kilometres from Cherrybrook to Epping. At the Cherrybrook construction site, up to 75,000 tonnes of rock has been dug out to get to the tunnelling depth of 16 m to get Isabelle on her way. All crushed rock from tunnelling will be recycled, with none going to landfill.

The twin North West Rail Link tunnels are 29 metres deep on average but Isabelle will be one of the two TBMs digging to the deepest point 58 m beneath, Thompson's Corner at West Pennant Hills. TBM3 was named after four year old Isabelle Andersen by tunnel builders Thiess John Holland Dragados to represent the families of the 900 workers who will deliver the twin 15 kilometre tunnels between Bella Vista and Epping. In the image above, TBM3 Isabelle's 105 tonne circular cutter-head is lowered into place. The TBM's cutter-head is made up of 40 tungsten steel cutters, which will split the rock as she moves forward. Each cutter will be replaced approximately every three weeks as they wear down.

Isabelle will dig mostly through Sydney sandstone and shale at about 120 metres a week on average. 07.11.2014


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