Piles include many different types and materials. The following text discusses the more common types.

Timber bearing piles are usually straight tree trunks with the limbs and bark removed. These piles, if kept continuously wet, will last for centuries; however, they are used for low design loads because of their vulnerability to damage while they are being driven into the ground. The small end of the pile is called the tip; the larger end is called the butt. Timber piles range from 16 to 90 feet in length with a tip diameter of at least 6 inches. The butt diameter is seldom less than 12 inches. A steel bearing pile might be an H-pile (having an H-shaped cross section). These piles are usually used for driving to bedrock. A steel pile can also be a pipe pile with a circular cross section. A pipe pile can be either an open-end pile or a closed-end pile, depending on whether the bottom end is open or closed. Concrete piles, such as those shown in figure 1-10, may be either precast or cast in place. Most precast piles used today are pretensioned and are manufactured in established plants. These piles are made in square, cylindrical, or octagonal shapes. If they are being driven into soft or mucky soil, they are usually tapered. Cast-in-place piles are cast on the jobsite and are classified as shell type or shell-less type. The shell type is formed by driving a hollow steel tube (shell), with a closed end, into the ground and filling it with concrete. The shell-less type is formed by first driving a casing and core to the required depth. The core is removed and

is then the casing is filled with concrete. The casing removed, leaving the concrete in contact with the earth.