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Square Shaft Piles vs. Round Shaft Piles

August 29, 2014

Helical piles are an extremely versatile foundation element that has many uses.  Some common applications include supporting new foundations, supporting boardwalks/decks in wetland areas, anchoring telecom towers, and even repairing a settling foundation.  

The piles can be customized on many levels, including the number of bearing plates (helices), the diameter of the plates, even the shape of the plates can be modified.  The central shaft is another element of the pile customization; it can come in a variety of lengths and can be either a solid square bar or a round pipe shaft.   

In our opinion, round shaft piles are best for compressive applications for several reasons.  First of all, the pipe shafts are more rigid and provide much better resistance to buckling.  Also, the connection joints are much more stable than square shafts, which have some "looseness" at their connected sections.   

With that said, square shaft  "lead sections", which are the first piece with the helical blades, install more efficiently than round shafts for several reasons.  First of all, the plates have more bearing area on a square shaft, as it takes away less plate area when compared to a round shaft.    Also, the square shaft can better penetrate soils better as the bottom of the shaft (leading edge) is a relatively "sharp" point when compared to round shaft piles.  

In an ideal world, a helical pile should have a combination of both:   a square shaft lead section for it's efficiencies, and round shaft extensions to provide better structural stiffness in weak soils.     Some manufacturers offer this combination while others don't.  

Feel free to contact us if you have any questions about helical pier technology!