Helical piles are a very effective alternative to traditional foundation methods in many construction applications. They are used in new construction as a deep foundation, in situations where soil conditions prohibit the use of conventional piles and in repair and restoration of existing structures.
Why are helical piles used?
Helical piers consist of a shaft with one or more helix bearing blades which are welded to the end of the shaft. The number, thickness and diameter of the piles varies based on the program requirements and the expected loads to be supported.
In order for helical piles to perform well it is imperative that they are properly installed using a machine with the correct swing resistance, auxiliary hydraulic flow and pressure, reach and break-out force. A machine like a skid steer is simply not capable of achieving a professional installation. Hoyt and Clemence tested helical piles that were installed in an unprofessional manner, to those installed by proper equipment in a professional manner in the same soil at the same depth and found a 50% difference in performance in tension!
Pile design is a complex and highly specialized field. It is crucial that a geotechnical engineer conducts detailed site investigations and analyses prior to the selection of a foundation type. With this data, the piles can be correctly sized and correlated to their load bearing capacities. On high liability projects, on-site confirmatory load testing may be warranted in order to provide additional confidence in the installation and that the design criteria is being achieved.