Examples of uncased shaft are given in the American Concrete Institute (ACI) Manual of Concrete Practice (1986). Other terms used to describe the drilled shaft are “pier” or “caisson.” Large shafts greater then 36 inches in diameter are often called caissons. The term “pile” is commonly associated with driven deep foundations of relatively small diameter or cross section.
Figure 1-4. Drilled shaft details (1 in. = 25.4 mm)