Concrete piles as foundations in construction
There are two main types of concrete piles: in-place and precast foundations. The on-site fund pile is formed on the ground, in the position in which it is to be used. The precast pile is usually manufactured in a factory, where prestressing techniques can be used, and after curing, it is driven or grouted like a wood pile.
Cast-in-place piles are divided into two general groups, the shell type and the shellless type. Shell-type piles are made by first pushing a steel casing or casing into the ground, filling with concrete, and leaving the casing in place. The shell acts as a form and prevents mud and water from mixing with the concrete. The stories may or may not be reinforced, depending on the circumstances. Shell-type piles are useful where the soil is too soft to form a hole for an unlined pile or where the soil is difficult to compress and deform an unlined pile.
Tanks can be cylindrical or conical, with smooth or corrugated outer surfaces. One type of conical shell produced in sections is known as a stepped conical pile.
Precast concrete piles are typically manufactured in a casting yard under controlled conditions. This allows not only the development of high-strength concrete but also flexibility in design, reinforcement, length, etc.
Prefabricated reinforced piles are manufactured in round, square, hexagonal and octagonal shapes. Very long piles are made by casting reinforced hollow sections, usually 16 feet (4.8 m) in length, and joining the sections together using stressed steel cables.
Precast concrete piles generally need assistance when driving, especially in sand, and one method of providing assistance is to use a water jet. A type of prefabricated pile has been developed especially for installation by injection. It is conical, octagonal in cross section, and has one or two vertical grooves on each face. The center is hollow, allowing water to be forced downward to loosen the soil at the tip. The grooves allow injected water to return to the surface.
