Sometime referred to as drilled piers, bored piles are cast-in-place piles ranging from 600mm to 6000mm in diameter with depth that can reach down to 100 meters. Bored piles are installed by first removing the soil by a drilling process and then constructing the pile by placing concrete in the hole. The simplest form of construction consists of drilling an unlined or unprotected hole and filling it with concrete. Complications that may arise such as difficult ground conditions and the presence of ground water have led to the development of special drilling technologies. The choice of the correct drilling technology must be done in a way as to minimize disturbance of the surrounding soil. For cohesionless soils (sands, gravels, silts), whether under the water table or not, the pile borehole must be supported using steel casing or stabilizing muds such as bentonite suspension.
2.5 meter diameter off-shore piles for Del Pan Bridge