Pile foundations consist of piles that are dug into soil till a layer of stable soil is reached. Pile foundations transfer building load to the bearing ground with the greater bearing capacity. Pile foundations are useful in regions with unstable upper soil that may erode, or for large structures. Pile foundations are often required to resist lateral loading. Lateral loads come from a variety of sources including wind, earthquakes, waves, and ship impacts.
The lateral capacity of a pile is usually much smaller than the axial capacity and as a result groups of piles are often installed to increase the lateral capacity of the entire foundation system. When vertical or plumb pile groups do not provide sufficient lateral resistance the piles can be battered in order to mobilize some of the higher axial capacity to resist the lateral load.
Piles are relatively long, slender members that transmit foundation loads through soil strata of low bearing capacity to deeper soil or rock strata having a high bearing capacity. They are used when for economic, constructional or soil condition considerations it is desirable to transmit loads to strata beyond the practical reach of shallow foundations. In addition to supporting structures, piles are also used to anchor structures against uplift forces and to assist structures in resisting lateral and overturning forces.
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