Ground Screws or Helical Screws (Any experiences)

[mchhabria]

I was looking for any feedback or experience from ground mount using helical screws or ground screws. I am in PA.

Any feedback appreciated.

Thanks MLC

[solarix]

ive been trying for years to use ground screws, but most of them require major installation equipment and I can't get my P.E. to sign off on them because its hard to prove the pullout under various conditions. Only thing he will trust is the dead weight of concrete. Ground screws cost about as much as concrete, but are so much faster.

[SunEagle]

ive been trying for years to use ground screws, but most of them require major installation equipment and I can't get my P.E. to sign off on them because its hard to prove the pullout under various conditions. Only thing he will trust is the dead weight of concrete. Ground screws cost about as much as concrete, but are so much faster.

That is surprising since ground screws are used to anchor manufacturer and modular homes here in Florida and must meet some pretty high wind loading due to hurricanes.

I wonder why your PE will not sign off on them unless the wind load calculations exceed what the ground screws can prevent.

[J.P.M.]

ive been trying for years to use ground screws, but most of them require major installation equipment and I can't get my P.E. to sign off on them because its hard to prove the pullout under various conditions. Only thing he will trust is the dead weight of concrete. Ground screws cost about as much as concrete, but are so much faster.

Existing soil conditions, along with and perhaps more importantly, soil upset conditions from the installation of the foundation screws, and all that resulting uncertainty, make pullout load calcs/predictions, and to a lesser extent what occasional loads from wind will do to pile fixation a bit of a wild card.

Also, for a lot of analyses, often the structure's dead weigh will offset a good portion of a pullout load from a wind/seismic induced overturning moment, usually adding a bit of comfort/safety factor to the analysis as well as that larger mass acting as a bit of a vibration dampener, reducing any occasional load impulse(s) perhaps a bit before it gets to the screw. Solar arrays usually do not weigh enough to do much to offset or modify such loads.

Probably a matter of some engineering judgment. FWIW, civil/structural was not my claimed engineering licensure proficiency, but from what I know of wind/seismic design, I'd not be using screw piles if it was my design without a lot more information about soil conditions and probably a site visit.

[SunEagle]

Existing soil conditions, along with and perhaps more importantly, soil upset conditions from the installation of the foundation screws, and all that resulting uncertainty, make pullout load calcs/predictions, and to a lesser extent what occasional loads from wind will do to pile fixation a bit of a wild card.

Also, for a lot of analyses, often the structure's dead weigh will offset a good portion of a pullout load from a wind/seismic induced overturning moment, usually adding a bit of comfort/safety factor to the analysis as well as that larger mass acting as a bit of a vibration dampener, reducing any occasional load impulse(s) perhaps a bit before it gets to the screw. Solar arrays usually do not weigh enough to do much to offset or modify such loads.

Probably a matter of some engineering judgment. FWIW, civil/structural was not my claimed engineering licensure proficiency, but from what I know of wind/seismic design, I'd not be using screw piles if it was my design without a lot more information about soil conditions and probably a site visit.

Yeah. I guess those panels are more of a "kite" then a heavy 40ft manufactured home.

So unless those ground screws are in clay or are very very deep, concrete makes more sense to anchor a pv system.

[mchhabria]

I just had a chat with http://www.goliathtechpiles.com/our-piles/ and they said they will send me some calculations for my project. If anyone is interested i am happy to share. Best MLC

[SunEagle]

I just had a chat with http://www.goliathtechpiles.com/our-piles/ and they said they will send me some calculations for my project. If anyone is interested i am happy to share. Best MLC

Interesting hardware. The main drawback I see would be not being able to adjust the panel tilt for seasonal changes but if might work for a fixed tilt array.

The decision to use these may come down to the cost and approval from the permitting office.

[peakbagger]

They are quite popular for big fields I see going in Mass.

I used the same rigs under a house to resupport the footings on some marginal soil, worked great.

Not so good in Northern NH where the soil is 90%. rocks

[Sunking]

That is surprising since ground screws are used to anchor manufacturer and modular homes here in Florida and must meet some pretty high wind loading due to hurricanes..

Sounds logical to me. Who wants to live next to a trailer park? First hurricane, and they are gone, and your property value goes up.

[J.P.M.]

Sounds logical to me. Who wants to live next to a trailer park? First hurricane, and they are gone, and your property value goes up.

I thought trailer parks were only tornado magnets. I learn more every day.

[J.P.M.]

Yeah. I guess those panels are more of a "kite" then a heavy 40ft manufactured home.

So unless those ground screws are in clay or are very very deep, concrete makes more sense to anchor a pv system.

I don't doubt helical anchors can be effective in such applications and be made to work. My remarks were more from a design engineering perspective with perhaps some of the considerations that would make engineers a bit more cautious when using them for a design.

[Sunking]

I thought trailer parks were only tornado magnets. I learn more every day.

Yep add flood plains and railroad tracks.

Q. What does a Tornado and Redneck Divorce have in common?

A. Some poor SOB is going to loose a trailer house.

[bcroe]

I don't think you could use ground screws here. Next to the Rock River, there are too many rocks of all sizes
to just drive something in. Post holes were a big problem in 2013. For now holes have been taking the form
of trenches. When a big obstacle is struck, you can get in there and dig it out. Bruce Roe

[SunEagle]

I don't think you could use ground screws here. Next to the Rock River, there are too many rocks of all sizes
to just drive something in. Post holes were a big problem in 2013. For now holes have been taking the form
of trenches. When a big obstacle is struck, you can get in there and dig it out. Bruce Roe

I agree that the type of soil and geological consistency will determine which type of anchor is the best choice.

[mchhabria]

Here is the follow up. For my project ground mouth, 4 panel up landscape setup. Max height of pole 9 feet. Ground screws will not work as per goliath after they ran the numbers. Oh well .

Thank you everyone for your comments.
Best
MLC