Excavating adjacent to concrete cast-in-place friction piles

[north_man]

I've got a project where a client is looking to excavate adjacent to concrete friction piles. I understand that this can reduce the pile capacity even after fill material is removed and returned when relying on skin friction in design. Are there any resources or rules of thumb that you use in quantifying this reduction in capacity?

 

[milkshakelake]

Some friction piles would ignore the top 10', 15', or something like that, in calculations. We call that the cased zone. If you can get a hold of the original pile drawings, that would be a great place to start in determining if this is even a factor for you to consider.

 

[human909]

I've got a project where a client is looking to excavate adjacent to concrete friction piles. I understand that this can reduce the pile capacity even after fill material is removed and returned when relying on skin friction in design. Are there any resources or rules of thumb that you use in quantifying this reduction in capacity?

If you are not suitably compacting the soil in place (which would be hard and likely not practical). Then the rule of thumb is that the skin friction is ZERO.

However as said above by milkshakelake, most pile designs ignore the first XXXm of earth anyway.

The first question you should be asking is what % of the pile depth are you excavating. 5%, 10%, 50%?

 

[EngDM]

I agree with @milkshakelake. Only thing I would add is that sometimes for interior (heated) piles they allow you to go lower than top 10,15ft. I've seen 5ft for this application.

 

[haynewp]

I would consult with a geotech in the area for resources and/or evaluation.