# Construction/Piles

A pile is a long structural member that penetrates deep into the soil. Factors such as soil conditions and adjacent building are consider when determining weather a pile-supported foundation should be used. Soil conditions may be to unstable to allow a conventional deep excavation , or the proximity of adjacent buildings may limit the depth of a excavation.
Pile-driving rigs equipped with either a drop , mechanical, or vibratory hammer drive solid piles or casings into the ground. pressurized hydraulic fluid or diesel pistons are used as a power source for pile driving rigs. Mobile cranes equipped with specialized machinery and attachments may also be used to drive piles.
Bearing piles and friction piles are used to support foundations. bearings piles are more frequently used and are driven completely through the unstable soil layers to rest on firm load-bearing soil. Friction piles do not have to penetrate to load-bearing soil. They must only be driven to a point where there is adequate soil resistance and pressure against the pile to support the imposed load.
Piles are placed beneath grade beams supporting bearing walls. Grouped piles may also be placed beneath concrete caps that act as a base for load -bearing columns. A grouped pile is a collection of numerous piles driven in close arrangement. Grouped piles are used when columns provide the main structural support of a building and the column load exceeds the load-bearing capacity of an individual pile.
Pile are constructed of wood, steel, or concrete. Wood piles are the oldest type of pile used and support wharves, docks and other structures build over water. Steel piles placed beneath buildings are most often H-shaped or tubular. Both types are driven into the ground with a pile-driving rig.
H-shaped piles are used for foundation support and also in the construction of shoring around deep excavations. Although H-shaped piles are relatively expensive on a per foot basis, they have a number of advantages over other types of pilings. H-shaped piles are available in various sizes of roll shapes or structural steel plates welded together. They are made from high strength and/or corrosion-resistant steels and can penetrate to bedrock , where other piles would be destroyed during pile driving.Tubular piles( pipe pile) may be filled with concrete after they have been driven. Tubular piles are a series of drill bits added to the pile-driving rig as the depth increases. When the specified is reached , concrete is pumped into the bottom of the tubular pile.Once the pile is filled with concrete , the tubular pile are raised and removed
Concrete piles are commonly used beneath foundations of heavy concrete structures. They may be precast or cast in place. Precast pile are commonly fabricated in a plant and heavily reinforced with rebar or prestressed cables. Precast piles are delivered to the job sire by truck and are driven into place with a pile-driving rig.
A mircopile, also known as a minipile, is a small diameter(3" to 12" ) drilled and grouted pile. Mircopiles consist pf high-strength cement grout and steel reinforcement and have designs loads ranging from 3 tons to over 500tons. Mircopiles can extend to depths of 200'. They may be used individually or grouped together. single or multiple rebar , threaded rod, post -tensioning strands are used as reinforcement. In some situations, the reinforcement may be post-tensioned to increase strength. Mircopiles serve many purposes, but their most important functions are foundation support, earth retention, and stabilization.