Types and classification of foundation piles

Piles can be classified by pile material, placement method, and load transfer method. Pile sections are made of traditional building materials: wood, steel and concrete. They can be composite in nature, using different materials for different portions of the pile. A pile with a wooden bottom section and a concrete top section is the most common composite type.

There are generally four methods or means used to install piles. These methods include driving the piles with a pile driver, injecting the pile using water jets, drilling and pumping concrete, and vibrating the pile in place. Sections of wood, steel and precast concrete are driven; Concrete piles and caissons are placed in pre-drilled shafts that may or may not be lined with steel casings. Bored concrete piles are drilled using a hollow stem auger through which concrete is pumped as the auger is removed. The type of pile placement is generally determined by the soil conditions at the site and the magnitude of the loads that must be supported.

When considering load transfer characteristics, there are four variations: bearing piles, friction piles, friction plus bearing, and sheet piles. The bearing pile transfers loads through the unstable surface soils to the denser, more stable soils below. Loads are transported vertically through the pile, and the bearing capacity of the pile depends on the final cross-sectional area and the strength of the material on which it is supported. Bedrock is generally considered the ideal material for supporting piles; However, this is often impractical due to depth, and less dense material must be used as a support medium. To increase the loading capacity of charging piles, their ends can be "chamfered" to increase the loading area of the end.

Parts of a foundation pile

Regardless of the type of material they are made of, all pile sections have certain basic parts. The following definitions apply to any code of this type:

• Head: the upper part in final position.
• Foot: the lower part in final position.
• Tip: the small end before or after placing it in position.
• Stock: The large end before or after being placed in position.
• Pile Ring: A wrought iron or steel hoop placed on the head of the pile to prevent cracking, spalling, or splitting.
• Driving Head: A device placed on the head of a pile to receive hammer blows and protect it from injury while driving.
• Pile Cut: The portion of the pile that is removed after driving is completed.
• Pile Shoe: A metal cone placed on the tip of a pile to protect it from cracking or fracturing.