helical piles and micropiles
helical piles and micropiles
(OP)
How would one support new steel column loads up to about 20 kips (unfactored) per column (supports only 1 storey; there are about 5 such new columns total), in an existing parking garage basement, where the soil may be weak below a stiff upper crust of clay under the existing 5" slab-on-grade?
Which would be used, helical piles or micropiles (clear storey height is 9'-6")?
What is the number of helical piles that should be used? 2 per column? 3 per column?
What is the detail for the top of the piles? A concrete cap extending some minimum distance beyond the pile, and of some minimal depth?






RE: helical piles and micropiles
RE: helical piles and micropiles
RE: helical piles and micropiles
RE: helical piles and micropiles
Caltrans has good details, also (but no helicals).
RE: helical piles and micropiles
I have concerns about helical pile durability and generally only consider them for residential applications. In any sort of commercial or high end residential application, I use minipiles.
Your column loads are small. So my guess is you will be governed by min pile requirements as I mentioned above.
Obviously piling is expensive and you are not sure about soil conditions below this 'upper crust'. You should probably request a geotechnical investigation to confirm that piles are warranted. How has the sog fared? That may hint at whether shallow foundations are possible.
RE: helical piles and micropiles
RE: helical piles and micropiles
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: helical piles and micropiles
I've only used micropiles in very tight areas. I thought they were more of a boutique type system (works well in specific applications, but not for a big project). And helical piles are propietary, good for uplift (tension), but once again not for the big projects.
RE: helical piles and micropiles
He noted the overhead clearance is limited.
Mini piles are also useful for deep foundations in karst topography (swiss cheese limestone) or where boulders might be encountered (moraines). The small size is easier to drill through those interferences.
RE: helical piles and micropiles