Pile to Base Slab Connection

[waytsh]

Simple question. (Or maybe not) Is it acceptable to have an auger cast pile that is not "sunk" into the base slab but merely connected to the base slab via hooked rebar? Do any of the codes prohibit a flush connection when both components are cast in place?

 

[J1D]

What’s the “base slab”? Pile cap? Not to my knowledge any code prohibits flush connection between pile and pilecap. With flush connection you have less connection fixity (this may not be a problem for a slab). For good fixity, sunken connection is more popular.

 

[JAE]

One aspect of "sinking" a pile may be similar to what happens with drilled piers. Usually, the top few inches of a drilled pier have very rough finishes, if any at all, with even dirt or debris mixing in with the top strata.

I used to have a note requiring the contractor to place concrete in the piers to a level 2" higher than required, and then later chip off the top 2" to remove this "bad concrete".

For an auger cast pile, the top strata of concrete/grout can be loose, higher in water content (due to rising water) and may be damaged by subsequent excavations around the pile top. Sinking this in a cap of concrete for 4 to 6 inches simply helps confine this concrete and minimizes crushing and settlement.

 

[waytsh]

The base slab is 24" thick cast-in-place R.C. The drop cap is 24"x24"x4" thick. I do not need to rely on the piles for any fixity. They are only required to take a lateral seismic load of a little over 2 kips. I was going to transfer this lateral force via hooked bars. It will keep things simpler in the field if I can avoid having to clean out around the piles to create the sunken condition. I just wanted to be sure I wasn't missing some code requirements.

Thanks for the response.

 

[waytsh]

Good point JAE, I will check with the pile installer to see what their procedure is regarding the preparation of the top of the pile.