Earth Anchor holding strength

[JCoastie]

This is unscientific, I'm not a physicist or engineer and didn't stay at a Holiday Inn Express last night.
I do however live in a hurricane area, and I use a lot of earth anchors to hold things down, sheds, greenhouses, trailer tie downs, etc.
I've seen things on the internet showing how easy they pull out and you should use this {insert more expensive thing here} instead.
Most tests I see, the anchor is installed and then pulled right out showing a few hundred pounds of holding force.

So I had a plan. I would install a single 32" single helix anchor with the 3" plate and measure the axial pull out force. I use a fair number in this size, and I also use longer 4" versions for larger things. The 3" plate is 3 inches up from the bottom, and the eye is 3 inches above ground level, so the holding plate was approx 26 inches in the ground, my ground soil, not yours, no clue how it will hold on your land lol

Then I'd install the same anchor and let it sit for 2+ months to let the disturbed ground harden up again and repeat the test to see if it improved.

This ended at step 1! I figured I'd see a couple hundred pounds, maybe 400lbs , 500-600 if I was lucky.

Well we saw 1800+lbs a few times, and the tractor was maxed out (even though the pic is ~1760)
I had to manually unscrew the anchor a few more inches before it finally pulled up and left a decent mound where it pulled the surrounding ground with it.
Very (happily) surprised!

 

[oldnslo]

I suspect like you that it varies a lot with soil type. How screwed in, I.e. Is down force applied while screwing it in or is it allowed to act line post hole auger and pull soil up. Also how long ground is left undisturbed before pulling, etc.

 

[JCoastie]

I use an impact wrench with a big socket to cheat when I drive them in, so a fair bit of my body weight when driving them in.

 

[kneedeep]

This is unscientific, I'm not a physicist or engineer and didn't stay at a Holiday Inn Express last night.
I do however live in a hurricane area, and I use a lot of earth anchors to hold things down, sheds, greenhouses, trailer tie downs, etc.
I've seen things on the internet showing how easy they pull out and you should use this {insert more expensive thing here} instead.
Most tests I see, the anchor is installed and then pulled right out showing a few hundred pounds of holding force.

So I had a plan. I would install a single 32" single helix anchor with the 3" plate and measure the axial pull out force. I use a fair number in this size, and I also use longer 4" versions for larger things. The 3" plate is 3 inches up from the bottom, and the eye is 3 inches above ground level, so the holding plate was approx 26 inches in the ground, my ground soil, not yours, no clue how it will hold on your land lol

Then I'd install the same anchor and let it sit for 2+ months to let the disturbed ground harden up again and repeat the test to see if it improved.

This ended at step 1! I figured I'd see a couple hundred pounds, maybe 400lbs , 500-600 if I was lucky.

Well we saw 1800+lbs a few times, and the tractor was maxed out (even though the pic is ~1760)
I had to manually unscrew the anchor a few more inches before it finally pulled up and left a decent mound where it pulled the surrounding ground with it.
Very (happily) surprised!

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I use the same anchors for my elevated shooting houses.
One in the middle under the stand.
When I do move them, usually have to dig the anchor out with backhoe.
After couple years, they won't pull out.

 

[greenie]

We tried to pull out power line pole anchor from a 1930's line that had been abandoned. We had a full sized Volvo excavator (I can't recall the model or weight) and tried to pull the anchor out so it wouldn't be a mowing or trip hazard. It wouldn't budge - and if aliens ever wanted to tow the earth out of orbit that would have been the place to hook the chain to.

 

[Joel/ak]

Anything man does to secure a structure is better than nothing but after living in AK and seeing results of numerous big earthquakes, if God wants it to move, it will. Same with tornadoes, hurricanes, etc.

 

[jonsstihl]

I have seen the power company put those power pole anchors in. I don't know if they have different types but the one I saw must have been atleast 8ft long probably more like 10 feet and drilled into the ground all the way. Cant really remember what the end going into the ground looked like but it is no wonder you can't pull them out. the pole would snap before the anchor would pull out.

 

[5030]

I use the ones sold by Farm Tec in their catalog and they are the commercial ones and come in various lengths and diameters but it still depends a lot on the soil you drive them into as well. The Farm tec ones come with drive tangs on top so you can mate them to a big impact wrench if you want to. I used my air powered IR 3/4" drive commercial lug nut wrench to drive mine in and it took every bit of it's 2100 foot pounds of torque to plant them. Talk about a vibration job, there it was, in spades. Won't do that again and don't have to.

 

[Williy]

When I purchased some there were several and
every one had the strength listed for each one so
check were you purchased yours so you know for
sure what you have

willy