GFWAust excavated a 150m long trench, 2m deep and 2m wide, in hard granite using PCF

Kembla Grange is a southern suburb of Wollongong, lying in the shadows Illawarra Escarpment. The site at Canterbury Road is a basalt outcrop adjacent to Northcliffe Drive, which has been extensively quarried for many years.

The site is being developed by Independent cement as a new warehouse. The warehouse construction consists of precast panels on a steel frame founded in shallow footings on the bedrock. A 2m deep drainage trench was required around the perimeter of the building. The rock is generally too hard to rip or break with a hydraulic hammer and blasting is not allowed in the Woolongong area. GFWAust excavated the 2m deep trench using PCF whilst the building was being constructed.

PCF or Penetrating Cone Fracture, is a non explosive means of rock breaking with low ground vibrations and air blast, and minimal flyrock. It breaks hard rock and concrete by burning a propellant to generate high-pressure gas at the lower point of a drill hole.  This pressurised gas is forced into micro fractures formed in the rock by the percussive drilling process. The expanding gas initiates fracture in a characteristic cone pattern, which breaks the rock away from the rock mass.

The trench was successfully completed economically and on time in very difficult circumstances.