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Re: Friction resistance of drilled piers & UBC Table 18-I-A

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There is a good reference in Foundation Design by Donald P. Coduto on skin
friction of piles and it is very comprehensive.  From a practical stand
point that I see in most soil's report, soil friction for piles are
generally around 500Psf and if the pile is subject to uplift, the value is
reduced by half.  As far as the pile supporting vertical load on sloped
ground, there will be a lateral load component on the pile or caisson that
need to be addressed for latereal stability.  The options are generally a
flag pole design or a grid system of grade beams tie in two direction for
the pole/pier/ caisson.  Sloped ground that are sensitive to creep should
have Caissons embeded into rock with interconnection by grade beams.  Few
years ago, a house foundation gave away to slope failure where the faulure
plane was located below the pier/caisson depth and therefore, the piers
could not offer any lateral stability to the structure.  This particular
site was in Laguna Beach, CA. I hope this answer some of your concerns, but
as with all soils, local abnormalities could lie within any given soils or
strata and at any given depth.
Good luck in your design effort.
Samir Ghosn, PE
Harris & Associates
At 12:57 PM 11/13/2002 -0800, you wrote:
> For posts/piers embedded in ground, UBC 1806.8.2.3 says: calculate
>vertical capacity using allowable soil-bearing pressure from Table 18-I-A.
>Does this mean the friction resistance should be ignored?  If not, where
>can I find nominal friction capacity (per unit area of pier surface) in
>absense of a soil report? Could anybody point me to a good reference. Load
>to be supported is about 6000 lbs, ground has some slope, and contractor
>perfers piers rather than pad footings. Thanks.
>Do you Yahoo!?
> U2 on LAUNCH - Exclusive medley 

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