minimum penetration on drilled pier

[COEngineeer]

The soil report say to penetrate the bedrock minimum 10ft. The minimum dead load on these piers should be at least 15000 psf. Can I use the minimum penetration skin friction to counteract the 15000 uplift OR do I need to go deeper?

Never, but never question engineer's judgement

 

[PEinc]

You really need to talk to the geotech who wrote the report. He can give you info on allowable side friction and end bearing. Does your drilled shaft weigh more than the 15000# uplift? If the shaft is below the water table, you will need the check its buoyany weight.

 

[COEngineeer]

No it doesnt weigh more than the min DL.

Never, but never question engineer's judgement

 

[PEinc]

To resist the uplift, sometimes it is cheaper to dowel or tie down the shaft rather than to extend the large diameter shaft deeper into bedrock. However, I would assume that a large diameter shaft drilled 10' minimum into bedrock would have sufficient side friction to resist 15k uplift. You would also need to check mass stability of the shear cone. The concrete to rock bond may be strong enough for 15k but the cone of possibly, highly fractured rock and soil would need to be checked using, possibly using buoyant weight.