Frequently Asked Questions

Yes. Helical piles are typically supplied with terminations (i.e., new construction caps) that can accommodate compression loading and/or tension loading. Because of the bearing mechanism by which they develop their capacity, they are often considered to provide the same (or nearly the same) capacity in both compression and tension.

Because helical piles are end-bearing piles, the capacity of an individual helical pile is not expected to be affected by a seismic event – as they are likely to not be designed to bear in or upon soils that are susceptible to liquefaction, where liquefaction during a seismic event is a concern. In June 2020, the International Code Council Evaluation Service (ICC-ES) included the use of helical piles in Seismic Site Classes A through F, in their acceptance criteria AC358.

Drivecast screw displacement piles are fully encased grouted piles that utilize soil displacement methodology to advance the pile into the soil by rotation. The ultimate capacities of Drivecast piles are really only limited by the torque required for their installation, and the diameter of their outer grout column that can be established in a project site’s soils. CHANCE and the geotechnical engineers that exist within their distribution network can work to identify custom Drivecast configurations, if and when applicable. CHANCE regularly produces Drivecast piles with a 8.625-inch O.D. and displacement assemblies intended to establish a surrounding 14-inch diameter grout column – and these piles can be considered for ultimate capacities on the order of ± 800 kips (400 tons). Larger shaft sizes and grout column diameters are available for consideration.

Helical piles are ideal for foundation support when they can terminate and be founded within or upon medium dense soils, or better, or weathered rock. Helical piles are not intended to penetrate intact rock.

Ideally, obstructions on a project site are infrequent. If and when they occur, an individual pile can possibly be relocated or battered (i.e., installed at an angle) to avoid the obstruction – or if the obstruction is quite large and potentially impacts several neighboring pile locations, mitigation can be explored to remove the obstruction (i.e., excavation near the ground surface, or pre-augering). Load testing of a pile that has encountered the obstruction is also an option, to verify if an isolated obstruction impacts the helical pile’s load- supporting capability. Read more about what to do if you encounter an obstruction.

Yes. Battered piles are most effective when they are installed at a batter angle of 45 degrees or less, from vertical. Battered piles are often installed in pairs to resist lateral loads applied along the same plane as the pile pair. This is important to consider, especially with small-diameter piles that are not anticipated to behave perfectly rigidly. It is better practice to use vertical helical piles for vertical loads, and battered piles (in pairs) to resist only lateral loads. The batter angle should be minimized if the battered piles are required to resist both vertical and lateral loads.

The life expectancy of a helical pile is indefinite, from a material perspective. However, all steel – even when galvanized – is subject to corrosion over time. The amount of corrosion (and steel loss) over time can be reasonably estimated with site-specific information on the electrochemical properties of a site’s soil. In absence of site-specific data, a pile type/size can be identified – and a conservative amount of steel corrosion/loss assumed – such that there remains adequate steel [cross-sectional] area to support design loading over the pile’s intended design life. Learn more about how corrosion impacts the service life of helical piles and anchors.

[Generally] Taken from CHANCE™ Technical Design Manual ed. 4: “In 1833, the helical pile was originally patented as a “screw pile” by English inventor Alexander Mitchell. Soon after, he installed screw piles to support lighthouses in tidal basins of England. The concept was also used for lighthouses off the coasts of Maryland, Delaware and Florida. Innovations of the helical pile/anchor have been advanced by both its academic and commercial advocates. Considerable research has been…” performed or assisted by CHANCE (formerly the A.B. Chance Company) - a brand of Hubbell Power Systems, Inc. (Hubbell) Today, contributions of financial, material and engineering support for research ventures related to helical piles is continued by Hubbell.

Helical piles are continuously evolving to include larger shaft sizes and larger lead (bottom) helix plate configurations. With the development of larger helical pile sizes, they’re competitiveness against cased micropiles and reinforced CFA/auger cast piles is increasing. However, larger helical pile sizes that can support significantly high loads also means greater torque requirements for their installation. One of the great appeals of common-size helical piles (e.g., 8.625-inch diameter or less) is their general ability to be installed with equipment that is significantly smaller [and therefore, cheaper to mobilize and operate] than that required for micropiles and CFA piles.