Pile cap with lateral

[COEngineeer]

I am designing a pile cap that will bridge a series of 12" dia. drilled piers that support a 3 sided culvert. If I have a horizontal reaction from the structure, can you resist this horizontal reaction with the passive pressure againts the pile cap? Or do I need to make sure the piers can take the shear?

This is an old project that was never built and it came back to life. Someone already designed it and the piers only have #3 @ 1'-0" O.C. So I am pretty sure it was not designed to take lateral. What do you sharks think?

Never, but never question engineer's judgment

 

[ishvaaag]

You should revise what is the situation by the standing code or codes. There's nothing bad in using friction and passive reaction except that scour may appear at some time. Being in the position to redesign the thing, one would use the piers.

 

[DaveAtkins]

Is there a geotechnical consultant on the project? He would be able to answer this question, but it is not at all unusual to use passive resistance against the pile cap combined with some resistance in the piers.

DaveAtkins

 

[ATSE]

Adequate lateral resistance is a common problem for laterally loaded pile caps.
To "activate" passive resistance requires a bit of lateral displacement. That same displacement must be tolerated by the pile. You need confinement for curvatures and high shears, and 12" spiral spacing is not adequate for confinement.
A simplified lateral analysis with elastic soil springs is a minimum, or a more high-powered Lpile analysis would be preferred. You need to be care you don't rely too heavily on passive soil resistance, and make sure the pile has sufficient strength, stiffness, and ductility assuming a lower bound p-y curve for the soil.
Good luck.

 

[COEngineeer]

OK, thank you folks.

This makes me wonder of all the designs I did when I was in residential market. We had tiny drilled piers with #3 @ 24" O.C.ties and very little passive pressure surface.

Never, but never question engineer's judgment