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Glossary of Piledriving and Foundation Construction Terms

Welcome to the APE Gloassary for piledriving and foundation construction terms. This is a great place to look for terms that you may be unfamiliar with when working with or researching piledriving technologies. This glossary also contains terms unrelated to piledriving, but that are frequently used on and around foundation construction projects. If you have a question or have term that you would like to add and do not know who to call please contact the APE Headquarters in Washington at (800) 248-8498. Business hours are from 8:00 AM to 5:00 PM Pacific Time. For less immediate inquiries, or if you would like an APE sales representitive to get in contact with you, please visit the APE Contact Request Form.

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Letter U

U Lead See Box Lead.
Ultimate Bearing Value of Pile 1. The maximum load which a single pile will support.
2. A load such that any increase will cause objectionable progressive settlement of the pile.
Ultimate Bearing Value of Pile Foundation The maximum load, computed as a total load or as a load per pile, which the foundation will support without objectionable progressive movement. See Safe Load.
Ultrasonic Testing Method of testing structural integrity of a pile. High frequency waves are transmitted to the pile and time required for a reflected wave to return to the top of the pile is measured.
Uncased Concrete Pile A column of concrete placed and left in the ground without encasement. See Augered Pile.
Uncased Pile Pile formed by drilling a hole into the ground and filling the hole with concrete without using a liner or tube. May be reinforced.
Under-Ream Enlargement of the lower end of an augered or drilled pile, shaft or caisson to increase its bearing area. Also called Bell.
Underhung Leads Pile hammer leads that hang from the crane boom by way of straps or cables.
Underpinning Piles, piers, walls, sheet piling, or other supports added to or replacing foundations under an existing structure to preserve the integrity of the structure or increase its load capacity.
Underwater Driving Driving a pile underwater by operating the hammer under water. Provision must be made for exhaust to the atmosphere for air or steam powered hammers.
Unit Weight The weight per unit volume of a material such as soil, water, concrete, etc. Typically expressed as pounds per cubic foot, grams per cubic centimeter, or kilograms per cubic meter.
Uplift Capacity The resistance of piles to pulling out of the ground. The ability of a pile to resist uplift and overturn forces due to wind and hydrostatic pressure. See Anchor Pile.

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