Machinery for the new tunnel excavation system is expected to arrive in Australia in early 2012, and trials are scheduled for completion by the end of 2012. The system will be 64 m long and will have a maximum boring diameter of 6 m and minimum tunnel excavation dimensions of 5 m by 5 m. After the trial, the technology is destined for use in other Rio Tinto underground mining operations internationally.

John McGagh, Rio Tinto’s Head of Innovation, said the test program at Northparkes offers the possibility for a “stepchange improvement” over conventional drill and blast practices “Depending on rock conditions, this system should provide capability to excavate at more than double the rate of conventional methods. For example, in a typical deep copper ore body, the rate of horizontal tunneling could be as high as 10 to 13 meters a day using this new system.

“This system incorporates continuous mechanical rock excavation that will not damage new tunnel walls, while still providing the ability to mechanically install ground support in parallel with tunnel advance. Importantly for Rio Tinto, it provides an opportunity to introduce fundamentally safer processes into the underground mining industry.”

Northparkes operations include both underground block cave mines and open cut mines. The underground mines were the first in Australia to use a variation of block cave mining. The mines produced 29,000 mt of copper in concentrates during the first three calendar quarters of 2010.