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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 N

N Value, SPT Value The number of blows required to drive a 2 in. O.D., 1 3/8 in. I.D, 24 in. long, split soil sampling spoon one foot with a 140 lb. weight freely falling 30 in. The count is recorded for each of three 6 in. increments. The sum of the second and third increments are taken as the N Value in blows per foot. (See ASTM D1586 - The Standard Penetration Test.)
Necking Reduction in area of cast-in-place concrete in a pile, either uncased or thin cased due to soil pressure or improper method of installation.
Needle Beam A structural beam inserted through a hole in a wall to support the wall during underpinning, jacking or excavating operations beneath it. The beam transfers the wall load to a temporary or a newly installed foundation.
Needle Gauge A pressure guage with a needle stem for measuring air or steam pressure in pressure hose, by puncturing the wall of the hose with the needle stem.
Needle Gun A hand held tool with a group of wired or needles in the end that vibrate when on and is used to clean a weld by beating the slag or covering from the welded area.
Needle Piles Very small diameter slender driven steel tubular or rail section piles used in underpinning operations.
Negative Batter See Aft Batter.
Negative Skin Friction 1. Side frictiona long a pile surface directed downward.
2. Effect of settling soil that grips a pile by friction and adds a downward weight to the structure load. Also called Downdrag.
Net Settlement See Settlement, Net.
Non-Displacement Piles Piles formed by boring or other methods of excavation. H, open-end pipe and sheet piles are considered low-displacement piles.

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