If you're looking for information on helical piers, you've come to the right place. Helical piers are a common type of foundation pier used in both residential and commercial construction. Please note that there is no difference between helical piers and helical pile foundations. Both terms refer to steel shafts with helical blades that are driven into the ground to provide structural support.
In this article, we will discuss what helical piers are, how they work, the installation procedure, applications, advantages, and limitations.
What are Helical Piers?
Definition: Helical piers are deep foundation elements consisting of steel shafts fitted with helically-shaped bearing plates (blades) that are mechanically screwed into the ground to transfer structural loads to competent soil or rock layers.
They are installed using hydraulic rotary equipment and can support both new construction and existing structures. Helical piles are particularly useful where surface soils are weak, expansive, or compressible.
They are commonly used in areas with limited access, making them ideal for urban construction sites or retrofit works.
The helical piers come in a variety of shaft diameters depending on the design load. Common shaft sizes include 3/8 inch, 1/2 inch, and 5/8 inch solid square shafts. The piers are also available in different load capacities depending on project requirements.
How do Helical Piers Work?
Helical piers transfer structural loads from unstable near-surface soils to deeper stable strata. The helically-shaped plates function like screw threads, allowing the pier to advance into the ground with minimal soil disturbance.
The load transfer mechanism may occur through:
- End bearing on competent soil layers
- Skin friction along the shaft
- Combination of both mechanisms
Installation torque is monitored during installation. The achieved torque value correlates with the load-bearing capacity of the pile, providing immediate verification of performance.
How to Install Helical Piers?
Followings are the stages followed during helical pier installation:
Excavation
The installation location is excavated to expose the foundation area where the bracket will be attached.
Positioning and Rotation
The helical pier is positioned vertically and rotated into the soil using hydraulic equipment.
Advancement to Design Depth
The pier is advanced until the required torque or design depth is achieved, indicating sufficient load capacity.
Bracket Installation
A foundation bracket is attached to connect the pier to the structure.
Load Transfer
The structural load is transferred to the pier using hydraulic jacks.
Backfilling
The excavation is backfilled and compacted to complete the installation.
When Should Helical Pier Foundation be Used?
Helical piers are suitable when:
- Soil has low bearing capacity
- Foundation settlement has occurred
- Construction access is limited
- Vibration-sensitive structures are nearby
Residential applications include new homes, additions, decks, porches, garages, and foundation repairs.
Commercial applications include office buildings, industrial structures, cell towers, and wind turbines.
Advantages of Helical Piers
- Minimal ground disturbance: Screwing action causes limited soil displacement.
- Rapid installation: Often completed within a single day.
- Immediate load capacity: No curing time required.
- Cost-effective: Reduced excavation and restoration costs.
- All-weather installation: Can be installed in various weather conditions.
- Removable and reusable: Can be extracted if necessary.
- Suitable for retrofit projects: Effective for underpinning and repair works.
Limitations of Helical Piles
- Load capacity depends on installation torque.
- Installation depth is limited by shaft length.
- Not ideal for extremely soft or organic soils without modification.
- Corrosion protection may be required in aggressive soils.
Helical piers provide a reliable deep foundation solution for both new construction and remedial works. Their quick installation, minimal disturbance, and verified load capacity make them a preferred option in many geotechnical conditions.