ABSTRACT
Knowledge of the geology of ground to be excavated is most desirable and should be considered essential for ensuring the safety of personnel who will work below ground level. The common methods used for creating a hole in the ground are, drilling, augering, machine boring, blasting, scraping, ripping and digging. Each relies for its success on the ability of the method to break and disaggregate rock and soil. The majority of drills are either percussive or rotary. In percussive drilling a chisel-shaped bit is repeatedly struck against the rock so as to form a hole. Large diameter machines may be used to bore tunnels. They are an extension of drilling technology and carry, at their head, cutters capable of breaking and excavating the ground. Augers are frequently used to drill through thick overburden prior to drilling the rock beneath, for drilling weak rocks, and for excavating large holes for cast piles and similar structures.
