How a helical pier works – Take “flight” with Helical Piers
Posted by Jonathan Maguire on Thu, Apr 08, 2010
This post will help describe how a helical pier works. Helical piers are used for foundation repair projects as well as new construction projects in poor soils. A helical pier is a round or square metal shaft with flights or helixes. What is a flight? It’s a steel plate welded onto the main shaft of a helical anchor (see picture). These plates are generally 3/8-1/2″ in thickness and have a pitch of 3″. This pitch allows the helical anchor to advance into the soil 3″ per revolution or 4 revolutions per foot.
How many flights or helixes are needed? Great question and there is no definitive answer for all applications. On a standard residential project where the loading is 10-30,000 lbs, one-two plates will work (each plate can handle between 20-25,000 lbs/ea depending on the manufacturer). Adding flights can increase the surface area that is made with soil and multiple flights decrease the loading required on each flight. We have found that adding flights can also help us install the product better as you have two or more flights pulling a helical into a the ground instead of just one single.
In part two of this blog, I’ll give some insight into how adding flights helps, and what are the limiting factors of helical pier capacities.