ABSTRACT
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A drilled pier, or a drilled caisson, is a cylindrical column that has essentially the same function as piles. The drilled pier foundation is used to transfer the structural load from the upper unstable soils to the lower firm stratum. The use of piers covers a wide range of possibilities, including these:
1. Drilling into bedrock for supporting a high column load 2. Transferring a bridge load to a level below that of the deepest scour 3. Friction piers bottomed on stiff clays for supporting a light structure 4. Belled piers bottomed on granular soils for supporting a medium column
load
5. Long, small-diameter piers drilled into a zone unaffected by moisture change in swelling soil areas
6. For structures transmitting horizontal or inclined loading
Essentially, piers and piles serve the same purpose. The distinction is based on the method of installation. A pile is installed by driving and a pier by auger drilling. A single pier is generally used to support the column load while a pile group must be used.
