Essential Terms in Helical Pile Design & Installation | Helical Glossary
- Product Family IDEAL
- Subcategory ELEMENT
- TIP Category DESIGN
- Tags HELICAL
TIP Description
Listed below is a glossary of terms related to helical design and helical installation.
Get Acquainted with Helical Product Terms
- 1. Anchor (Tie-back) – For resisting upward forces, lateral forces, and
overturn movements. A helical unit in tension is an anchor or tie-back
(A helical unit in compression is a pile or pier). - 2.Axial Load – Load in line with axis of pile.
- 3.Batter Pile – Pile driven at an angle. Often to reduce lateral forces.
- 4.Bearing Stratum – Any soil layer which provides a significant portion of
the axial load capacity by applying resistance to one or more of the
helical plates. - 5.Dead Load – The load of the structure with no outside forces acting on
it. - 6. Design Load – Dead Load plus Live Load. Also known as; Working
Load, Allowable Load, and Service Load. - 7.Effective Torsional Resistance – The average installation torque
typically taken over a distance equal to the last three feet of
installation or the last three diameters of penetration of the largest
helix plate. - 8. Fetch Up – Attaining specified torque with or without reaching glacial
till/bedrock. - 9.Flight Pitch – Distance from the top of the top end of a helix to the top
of the bottom end. - 10. Helix (pl. Helices) – A spiral-shaped steel plate extending out from the
shaft at a 90-degree angle at all points and traveling one
circumference of the shaft. (Plural form said he/less/seas). - 11. KIP – 1,000 lbs of force.
- 12. Live Load – The forces not calculated in a Dead Load. These forces
could include people, furniture, animals, cars, weather, machinery, etc. - 13. Load Overview – Dead Load + Live (Active) Load = Design (Working
or Allowable or Service) Load X Safety Factor (Usually 2 but don’t
assume) = Ultimate (Test) Load. - 14. Mechanical Strength – The maximum load resisted by the structural
elements of a helical pile without permanent deformation of the
element. - 15. Pier or Pile – To create a deep foundation where a shallow foundation
is not adequate. For new or existing structures. A helical unit in
compression is a pile or pier (A helical unit in tension is an anchor). - 16. Post Grouted – Placing Grout inside and installed pile. Pile typically has
a plugged leading end. - 17. Post Tensioned to Load – Using force to load an anchor. Usually when
there can be no movement under working conditions. Can be done on
every anchor when no movement is critical. - 18. Spin Out – Sitting on rock- end bearing- no real torque.
- 19. Static Load Test – Loading a pile under test conditions. Allowable
movement is dictated by engineering or building department.
Standard is ASTM D1143 for Compression. D3689 for Tension. - 20. Torque Correlation – The relationship between the force required for
installation and the Theoretical Ultimate capacity of the installed pile
(kips). - 21. Ultimate Load – Design (Working/Allowable/Service) Load multiplied
by a safety factor which is often 2. This is the need-to-know number. –
Sometimes called the Test Load or the Factored Load but be careful to
get clarification of the phrase “Factored”. “Factored” load may refer to
LRFD design philosophy which is not used for Helicals. - 22. Value Engineering (VE) – Designing in a cost-effective manner. Often
referring to a re-design with a more cost-effective solution.
