Abstract: Currently, the drilling and installation of the bored and castinplace reinforced concrete piles include positive circulation with slurry, reverse circulation with slurry, impact boring and allflight auger boring methods. The selection of an appropriate drilling method should comprehensively consider factors such as, subsurface conditions, environmental considerations, construction schedule and cost. The feasibility of positive circulation, reverse circulation and all flight auger boring methods, quality of borehole, and efficient of borehole installation and cost are comparatively evaluated. It is concluded that the reverse circulation method for upper cohesive soils and all flight auger boring method for the lower gravelly soils are the most cost effective combination approach.

Key words: Bored Piles, Positive Circulations, Reverse Circulations, All Flight Auger Boring, Combined Boring Methods