msucog
I am aware of the IBC Ch 18 note which states something to the effect that piers with an l/d ratio > 30 can be installed under the supervision of a geotechnical professional. I take this to be addressing constructability from the standpoint that the installation of deep slender piers...
In drilled pier design for compression loading, and in fairly uniform alluvial soils, I typically follow the FHWA recommendations for limiting the length:diameter ratio to be less than 30, adopting the rationale that load transfer below this depth attenuates.
Beyond the 1999 FHWA Drilled...
I have a question about a topic some of you may be tired of – subgrade modulus – but it does have some interesting features, and I hope someone may have some insight. We are providing recommendations to a structural engineer for modulus of subgrade reaction values beneath a 2.5-ft thick mat...
Focht,
I'm not sure I understand your concern about piers below the water table - is it a general concern, or is it due to the adjacent piers ? Generally speaking, I don't have any concerns about drilled piers below the water table - we routinely construct those very successfully. In this...
Thanks for your comments all. Unfortunately there is not room to make the new foundations as belled piers at the same tip as the existing bells, although I agree that this would be the preferable option. Neither is it practical to replace the existing piers.
The two options I was considering...
I'm reviewing a design for an addition to an existing structure. The original structure is supported on belled piers, about 12 feet deep and 10 feet in diameter, bearing on med dense to dense alluvium. The column loads of the addition are such that deep foundations are required, and 36-inch...
