PILE CONSTRUCTION

As a Builder, you will coordinate and direct pile-driving operation crews. Piles include many different types and materials. The more common types are covered next.

BEARING PILES

TIMBER BEARING PILES are usually straight tree trunks with the limbs and bark removed, and all timber will be PRESSURE-TREATED. 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.

STEEL BEARING PILES are usually H-pile (having an H-shaped cross section). These piles are usually used for driving through bedrock or until refusal. 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, as shown in figure 8-12, 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. When driven into soil 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 when the hollow steel tube (shell) with a closed end is driven into the ground and it is filled with concrete. The shell-less type is formed when first a casing and core are driven to the required depth. The core is removed, and the casing is filled with concrete. The casing is then removed, leaving the concrete in contact with the earth.

SHEET PILES

Sheet piles, made of wood, steel, or concrete, are equipped or constructed for edge-joining, so they can

Figure 8-12. - Types of concrete piles.

be driven edge-to-edge to form a continuous wall or bulkhead. A few common uses of sheet piles are as follows:

1. To resist lateral soil pressure as part of a temporary or permanent structure, such as a retaining wall

2. To construct cofferdams or structures built to exclude water from a construction area

3. To prevent slides and cave-ins in trenches or other excavations

The edges of steel sheetpiling are called INTERLOCKS (fig. 8-10), because they are shaped for locking the piles together edge-to-edge. The part of the pile between the interlocks is called the WEB.