Commercial Helical Pile Systems
Helical piles offer a steel foundation support system made up of a central shaft and one or more helix-shaped bearing plates. These bearing plates are often referred to as flights or blades. Each bearing plate is welded to the lead section.
Extension shafts are used on each pile to extend the pile to competent supporting soils and achieve design depth and capacity. Each extension shaft can be used with or without additional helical blades.
Brackets are used at the top of each pile to secure the pile to the structure. This setup makes helical piles appropriate for new construction and retrofit applications. After brackets are attached, helical piles are advanced or screwed into the ground.
Several terms are used interchangeably to describe this foundation support system, including:
- Helical piles
- Screw piles
- Helical piers
- Helical anchors
- Helix piers
- Helix anchors
The term “pier” most often refers to helical piles loaded in axial compression, while the word “anchor” most often refers to helical piles loaded in axial tension.
Design Considerations
The bearing of the helix blades against the soil generates most of the axial capacity of helical piles. Each blade is spaced three diameters apart to prevent a single blade from causing significant stress to the bearing soil. Every helical blade acts independently in bearing along the shaft.
Each pile has a center to center spacing at the helix depth of four times the diameter of the largest helical blade, at least (ICC-ES AC358). At the ground surface, the top of each pile may be closer but installed at a batter away from each other to meet spacing criteria at the helix depth.
For tension applications, the uppermost helical blade is installed to a depth of twelve diameters below the ground surface (ICC-ES AC358).
