piles on rock
piles on rock
(OP)
does a plug form in HP piles or pipe piles when pounding on rock, such that you can count on the entire area for end bearing?
thanks
thanks
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RE: piles on rock
Why not use the allowable structural strength of the pile if your rock is very competent.
RE: piles on rock
On rock with a relatively low compressive strength, it matters if you assume a plug or not (for instance, on 48"x1" cans).
I saw on one example that the designer assumed that a plug formed on the bottom of an HP 12 pile (pounded on rock) and therefore was able to use that entire area when calculating end bearing.
So i was just wondering if you assume a plug on the smaller pipes and H piles, but not on the larger ones, or if piles on rock were special and such you assumed the entire bottom area instead of just the area of steel for the bearing resistance.
thanks
RE: piles on rock
When dealing with piles on rock, you should do the required investigation and tests on rock cores to get a good idea of the bearing capacity of the rock. Be conservative and use the section area of the pile in the analyses so there are no nasty surprises. Otherwise assume friction on the "box" perimeter.
Jeff
RE: piles on rock
When you say "assume friction on the 'box' perimeter", are you talking about calculating the skin friction component?
I pretty much have done as you suggested, and am waiting on data from the lab for the compressive strength of the rock, but in the meantime, used a presumptive value to get rolling.
thanks
RE: piles on rock
Assuming that you had a plate at the bottom of your pile. The effect would be to allow for aa assumed uniformity of stress on your rock layer. If no plate high concentrations of stress would prevail that may have an effect on the rock capacity. For driving onto/into rock one needs to evaluate the driving stresses as piles should not be subjected to excessive stress. Limiting values are provided. This can be done using the WEAP analysis.
On the other hand if the pile was to be plugged through the overburden material and came to rest on the rock, I would probably not use the full end area.
No matter how you lookm at the problem, I would not want to use a load that exceeds the allowable structural capacity of the pile.
hence the beauty of pile design usig static analysis is the conjuring up of all these possible capacities, throwing them in a pot, and finally deciding which would be best for the witches final brew - geomagic, mumbo jumbo etc.
If you are looking for high capacity piles you may wish to look at a drilled shaft. However, this would depend on the conditions of your overburden soil.
Finally, are you providing the allowable load for the pile or is a load that is required to be taken ptrovided by the structural engineer. It make a difference sometimes.
Have fun
RE: piles on rock