David Lees and Associates were appointed by Brandrill Limited to provide engineering assistance in the development of their non-explosive rockbreaking technology, PCF, for Hawkesbury Sandstone. The technique uses a fast burning propellant to deliver a volume of high pressure gas which breaks the rock with nominal vibration, noise and flyrock.

The PCF (Penetrating Cone Fracture) has been shown to be highly effective in breaking concrete and homogenous rock types. The adaptation of this technique for the horizontally bedded Hawkesbury Sandstone was required for deep basement excavation and tunnel projects in Sydney.

Trials were carried out at a deep basement in the Sydney CBD to precondition the sandstone to assist mechanical excavation. Major trials are now being developed at a quarry northwest of Sydney to determine optimum drilling and charging techniques.