Posted on October 11, 2013
Helical Pile Installation
Helical Pile Installation – Observations129 Island View Dr., Lavallette, New Jersey
It is October 11th, 2013 and we are almost a year away from when Hurricane Sandy struck the east coast of the United States. We have accomplished many sets of plans for clients in different towns since the storm, but today it was finally time to install some helical piles on one of our damaged shore homes that is in the process of being elevated for flood hazard mitigation. What are helical piles, you ask? They look a little like an opener for the largest bottle of wine you would ever see. If you have absolutely no idea what they are check out this page, then come back here to read more.
Wolfe house lifters, lifted the house into the higher position and provided temporary cribbing (the wide, built up, wooden piers) to support the house while the new foundation is being installed.
The helical piles were provided by Magnum Piering, and being installed by Renova Structural Systems, as part of a ‘V-zone’ compliant foundation consisting of helical piles, a concrete grade beam (supported by the piles, and tying the piles together for lateral support), and masonry piers that support new engineered beams. This type of foundation is required in a high velocity flood zone, but is also recommended for coastal ‘A-zones’ as well.
The rain was intermittent in the middle of a slow moving Nor’easter that was buffeting us with 35 mph winds. I showed up at 9:30 a.m. ready to observe some installations, and although everything was laid out (leads, shaft extensions, and a drive head on the machine) there was nothing going on at the site. I donned my rain-suit, stowed my glassed and headed over to talk with the lead contractor on the job. The height clearance was so tight that the drive-head mounted on the machine didn’t fit under the sill plate to drive the pile, so the installer went to retrieve a smaller drive head that would get the job done.
After a two-hour delay, I was about about give up and head back to the office. I said my ‘goodbyes’ to everyone on site and headed to my car when the installers pulled up to the site with the new drive head. I thought to myself, “I should’ve just threatened to leave earlier and they would’ve shown up then!” So back to the job-site I went. After a few minutes of installing the new drive head they were ready to install the first pile.
Our design had the corner piles installed at a forty-five degree angle to the house, and a twenty degree batter angle into the soil. The reasons for the angles has to do with resisting lateral forces in different directions, but it is essential. Deep foundation elements are designed with a factor of safety ranging from two to three, but they should be installed as close to the plans as possible. The installers lined up the lead shaft in the corner, installed the drive head and pin, checked the angles, and started screwing the pile into the soil.
As they installed the pile, they were careful to check the angles as the pile inserted itself into the soft beach sand soil. When the first segment of pile was nearly fully inserted, they stopped the machine, bolted a new section onto the pile, and continued the installation. Our plans called for each pile to be installed to a minimum depth of sixteen feet, and a torque of 5kip-ft, and a bearing capacity of 20kips. The lead section is six feet long, and each extension is five feet long, allowing the minimum depth to be achieved with only three sections. As the last shaft was wound down into place the torque reading showed that the bearing capacity had reached a whopping 37 kips! That is nearly double the design capacity required.
Each pile installed is logged on a sheet showing the depth, pile series and number of helices, the torque rating, and bearing capacity. The piles receive a metal cap designed for a proper connection between the concrete grade-beam and the pile. Then it is time for the contractor to form out where the concrete beam is to be placed.
Yes, it is expensive. No, you don’t get to see this money after it is spent. It isn’t like granite counter tops. It does solve the problem of installing deep foundations where they are required, and it is impossible to move the house out of the way. If you think you need this kind of foundation, or you are just interested in getting more information about the process, call our office today at (732) 886-5290, or fill out a request for information form on our website, and I would be happy to share any information I have to help.
-Brian W. Penschow, Assoc. AIA