ABSTRACT
The most important characteristic of Hawkesbury Sandstone in the Sydney area is its enormous variability. The North Sydney area, a well known grave yard for the unwary excavation contractor. In a metropolitan environment the two main concerns for the contractors in preparing their tenders are Marketing of the Rock and the rock rippable. The ripped rock is loaded into trucks using traxcavators or hydraulic excavators. The trucks must be bogey drive as single axles will not handle the ramps. Track-type bulldozers of varying size with attached rippers are the conventional tools for loosening the rock. There is no doubt that rippability and the selection of the appropriate machine is a function of the rock strength. However, it is also clear that defect spacing within the rock and the rock's abrasiveness have a significant effect. On completion of the bulk excavation, and removal of the truck ramp, the contractor is generally faced with foundation excavation by use of hand held jackpicks.
