Foundation, Concrete and Earthquake Engineering

Laterally Loaded Drilled Piers

Drilled piers will be subject to large, lateral loads along the pier length in cases when piers are used as retaining walls, walls to arrest slope movement, power pole foundations, or anchors. Also, when the, earth pressures on the, basement walls are unequal or insufficient to resist the lateral loads from the superstructure, the, necessary resistance must be provided by the foundations. This condition occurs when there is no basement, when the depth of the basement walls below the ground surface is too shallow or when the lateral movements associated with the mobilization of adequate earth pressures are too large to be tolerated. The piers will then be loaded with lateral forces at the top, axial forces from overturning and, usually, moments at the top.
Seawall Reconstruction - Rio del Mar, Santa Cruz CA
The allowable pier head deflection in each design case, may be a few tenths of an inch or a few inches, depending on the project requirements.

Piers that must sustain lateral load can be,and have been, designed successfully, by approximate methods. The allowable lateral load on a vertical pier can be obtained from a table of presumptive values found in some handbooks, building codes, or from simplified solutions that assume a rigid pier and one soil type. However, these allowable loads may not be appropriate compared to values that may be computed by the recommended method herein and they provide no information on pier deflection. Use of simplified solutions may be, misleading for many drilled pier foundations.

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