How many times has a beautiful site for solar been negated due to
geotechnical findings of soft/organic or sandy soils. Soft organic soils can
cause pose quite an issue with solar projects.
They require deeper embedment depths and can significantly impact
A helical pile and a driven pile are
very different in how they perform in various soil conditions. A driven pile works off skin friction versus
a helical pile which has a spade/anchor at the end to create a cone of weight
to resist large pullout forces at shallow depths. Driven piles work well in soil that is
firm to provide high skin friction.
Whereas soil conditions such as soft/sandy
soils, saturated soil, and frost depth can impede soil friction reducing the
lateral and vertical bearing loads requiring deeper embedment depths.
Deeper embedment depths can
significantly affect project costs. In the Midwest with highly organic soils
combined with deep frost lines, and the Southeast with saturated and sandy
soils we have seen Geotechnical reports requiring a 15, 18 and even 20+ ft.
embedment depth for driven piles.
With APA’s helicals, we simply adjust
the size of our helix to match the soil conditions. APA does a
pullout and lateral test to determine the correct helical size and depth. Helix inserts come in many different sizes from 4 ¼” to 10”. A larger helical size from 6” to 8” is less
than $1,000 per MW. A second option
could be to provide a double helix. A
helix well matched to the site, will provide the balance of drivability and
handling to meet the site criteria.
The main feature of the helical anchor
is the helix. The helix is a solid anchor that holds the post firm in the
ground. The surface area of the bearing plate provides high pullout
resistance. Utilizing APA’s helical
anchors is very cost effective method for soft soils.
A good example of soft soils is Snow Hill, North Carolina. This
project was a 7MW project and was in extremely soft soils. The helical combated
these conditions and made the array a success. APA installed an 8 inch helix at
an embedment depth of 30 inches.
Another example was with a 7MW site in Redwing, MN. The soil was very
organic. The customer had a driven I-beam company test the site to see if the
driven pile system would work. We had heard that the piles had to go extremely
deep in order to get a required pull out value (assumed 15+ feet), and APA
helicals preformed really well at 70” with an 8” helix. APA was awarded and
completed that project in 2016.
APA Solar Racking has a solution for any soil type and makes it a
mission to put research and development as a top priority. Follow us on Social media and read our other
blogs today! We invite you to reach out to our sales team with any questions or
for a project quote.