Helical Pile resistance
Helical Pile resistance
(OP)
I am designing a foundation for a large arch building. The engineer who is designing the superstructure gave me reactions at the pedstals where the arches fall.
The horizontal loads are about 80k and in order to resist this horizontal load we are using battered helical piles. The soil is good, so the plan is to resist the vertical loads using a spread footing with the piles attached to resist the horizontal.
Is this possible? I need a better good batter to resist the horizontal load, and I am assuming the vetical component of the piles is resisting some of the vertical load and the rest is resisted by the soil bearing.
The owner does not want to use a truly pile supported foundation because of cost. The geotech also says that we should not count on passive pressure, but the soil is good enough for shallow foundations.
Does anyone have a good idea about how to model this?
The horizontal loads are about 80k and in order to resist this horizontal load we are using battered helical piles. The soil is good, so the plan is to resist the vertical loads using a spread footing with the piles attached to resist the horizontal.
Is this possible? I need a better good batter to resist the horizontal load, and I am assuming the vetical component of the piles is resisting some of the vertical load and the rest is resisted by the soil bearing.
The owner does not want to use a truly pile supported foundation because of cost. The geotech also says that we should not count on passive pressure, but the soil is good enough for shallow foundations.
Does anyone have a good idea about how to model this?






RE: Helical Pile resistance
RE: Helical Pile resistance
I would be carefull of this approach, as I think you will have a deflection compatability problem. The piles will be very stiff and intially attract most (if not all) of the vertical column load, where as little of the load will be taken by soil bearing as it is usually assumed that some settlement is required to develop the full bearing capacity of the soil.
I agree with SteelPE that, if possible, a tension tie might be a good solution here.
JMHO
RE: Helical Pile resistance
RE: Helical Pile resistance
I dont know why helical piles would not work also. I agree that they should only be there for horiz. thrust, not "some of the vertical load". Load attracts to the stiffest element.
Also, getting a steep enough batter to keep the upper stem of the helical pile from wanting to "bend and pull laterally through the upper layers of soil) might be practically difficult.
RE: Helical Pile resistance
I have seen the hairpin detail you are talking about. I have always been told that a hairpin would be used for small loads (<20k) anything greater and you would need to use a tie. I have also been told that they are very unreliable as they are rarely installed correctly. I try to avoid them whenever possible.
I'm not sure what others think but this is what I have been told.
RE: Helical Pile resistance
Surely, though, the best bet is to use the tie under ground and then just to support the building with conventional footings. The fact that the ties go for a long way surely can't equate to the costs of piling?