Friday, November 13, 2009

re: helical piles

My understanding of how helical pile design normally works is that it is like a pre-engineered truss or any other specialty structural item. Each pile contractor works with a manufacturer who usually has their own proprietary design, and they supply engineering in the form of load capacities, they have typical attachment details, supply their own brackets, etc. If you are the EOR of a new building or a repair to an existing foundation, you would likely tell them how often you would like these piles spaced along the footing and would give them the required load capacity. For residential applications, the piles will likely far exceed anything you can throw at it from a gravity load. Ensure that you have a say in approval of the contractor and that they have success in your area in the installation of this product in similar applications, I have heard some horror stories out there. This isn't drywall, it is a pretty complex operation with a lot of unknowns.

There are pluses and minuses to every type of foundation system. Use caution if it is an existing structure and you are doing repair work. Make sure a geotech has identified the soil issues. Use caution if you are partially underpinning part of the existing structure, make sure your existing structure can now carry the loads to the helical piles rather than being supported by uniform soil bearing pressure.

Andrew Kester, PE

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