ABSTRACT
Nomenclature .............................................................................................................................. 377 References ..................................................................................................................................... 377
Drilled shafts are cylindrical, cast-in-place concrete deep foundations poured into and formed by a bored (i.e., “drilled”) excavation (Figure 7.1). They can range from 2 to 30 ft in diameter and can exceed 300 ft in length. The term “drilled shaft” is synonymous with cast in situ piles, bored piles, rotary bored cast in situ piles, or simply shafts. Although once considered a specialty foundation for urban settings where vibrations could not be tolerated or where shallow foundations could not develop sufficient capacity, their use as structural support has recently increased because of heightened lateral strength requirements for bridge foundations and the ability of drilled shafts to resist such loads. They are particularly advantageous where enormous lateral loads from extreme event limit states govern bridge foundation design (i.e., vessel impact loads).
