helical piles

[struct_eeyore]

Hi all,

For those with experience with helical piles - I need to support a load of about 150K - the kicker is that I only have about 12' of width in which to place my equipment, and probably 12' height clearance. Is this something that can be done?

 

[PEinc]

Helical anchors and piles can be installed with hand-held drive equipment and also small equipment like Bob Cats and mini-excavators. A small drive head (about 5000 ft-lbs max. torque = about 40 to 50 kips ultimate capacity) is attached to a leg that prevents the drive head from spinning around so that the torque is applied to the helical shaft. This smaller drive head has relatively low torque . Therefore, the pile or anchor capacity is limited to less than would be available with a more powerful drive head attached to a bigger piece of equipment.

http://www.PeirceEngineering.com

 

[AskTooMuch]

We use helical piles a lot inside our plant. I'd say NO.

Excavator needs 10' clearance plus the length of helical piles which is 10' or 20' section normally = 20' or 30'.
If helical pile contractor use mini excavator and 5' helical piles length still maybe no (not sure about mini excavator clearance).
But you probably won't be using mini excavator if you want 150 kip.

16' is the minimum. 10' for excavator and 5' helical pile length + 1' extra.

 

[Agent666]

It's quite common to install the pile shaft in stages/segments, welding each stage once its screwed into ground level to address any overhead height issues. Then it just comes down to the clearances to the equipment itself, suggest talking to local contractors about capability.

 

[AskTooMuch]

It would be a mistake if you only consider the clearance of excavator and not add the length of helical piles per section in your clearance. I'm not guessing this. I asked our helical pile contractor and have seen this done in the field many times.

 

[Ron247]

I think the more common helicals used in my area are 7' long. They generally bid 14' as a start total length and increase cost in 7' increments

 

[darthsoilsguy2]

Yes. Helical piles have been used inside existing garages. The biggest problem will be finding the contractor set up to do it. Check out this photo, the pile extensions look like they are 5 ft. I don't have a photo of the equipment but it was a bob-cat mounted system.

 

[darthsoilsguy2]

to throw 1 more monkey wrench in the works... consider how you are going to load test the piles. the standard of care for deep ground improvements is to have proof testing done at the site.

 

[darthsoilsguy2]

Here's a photo of that same contractor using a mini-ex to install helicals on a different job. makes me wonder if they didn't use a bobcat mount as i remembered??... seems like this assembly would be pretty close to 12 ft clearance... but if the ground is open, you could shave off some dirt with bobcat first for clearance.

 

[PEinc]

I would ask a local installer or supplier about what hand-held installation equipment is available. A. B. Chance has or had a brochure with a photo of hand-held equipment for smaller helical anchors/piers. As I mentioned above, for one of my projects, a 5000 ft-lb drive head with a long attached steel tube (about 10' long) was used to install tieback anchors. The tube was attached to the drive head to stabilize the drive head and allow application of torque to the helical anchor's shaft. The end of the tube is placed against some immovable object, like a wall or a vehicle. As the drive head turns the shaft, the tube is resisted from spinning when the tube pushes against the wall or vehicle. The available anchor or pier capacity will be limited by the torque capacity of the smaller drive head.

http://www.PeirceEngineering.com

 

[TLHS]

As far as proof testing, it depends somewhat on the type of installation, type of loading and the required reliability. There are some reasonable correlations to installation torque as long as you have calibrated your factor of safety appropriately.

 

[Agent666]

In this part of the world, testing simply allows you to refine the strength reduction factor used in terms of design process. You can certainly get by with no testing, usually make sense if you have lots of piles where there would be a significant saving in going to a more refined design. Usually this means getting them to site twice though, once to do the tests early on, and then for the final install after design/fabrication, which isn't always a luxury you have.

Though testing tells you a lot of other useful things like deflection vs load behaviour. These things tend to move quite a bit to mobilise their ultimate capacity.

 

[Rabbit12]

They can use a drive head attached to a Bobcat; I've seen a video of them using it from one of our local installers. The particular piles they were installing in the video were 5-7' long I'd estimate. Based on that I'd think 12' would be no problem if you can get away with smaller 3" diameter or so piles.

Contact Helipile.

http://helipile.com/

I've worked with Randy a few times. He's got a network of installers and he'd be able to tell you if what you need is possible with helicals. I should add, although they are located in Denver they do work all over the US.