Drilled shaft foundations are a very established deep foundation technology. They are constructed typically by excavating a 3-12 ft in diameter hole and constructing a cast-in-place reinforced concrete foundation within the hole, typically by placing in the steel reinforcement and subsequently pouring in concrete (very commonly using Tremie pipes).
These foundation systems have excellent axial capacity due to a combination of side shearing and end bearing resistance. The size of the foundations also allows for significant resistance to lateral and overturning loads. Drilled commonly reach depths of up to 200 ft and may extend to 300 ft or more.
