Chipped Top of Pile

[KHoff]

I received an RFI regarding a chipped pile (see attached picture). It is a 16" diameter pile and is supporting approximately 45 kips, so it is a relatively lightly loaded pile. Consider the two options listed below:

1. Damaged part of pile is contained within the portion that is embedded in the grade beam above. Leave pile as is and pour the grade beam.
2. Trim top of pile flat, clean reinforcement of all concrete, and lower grade beam excavation in order to maintain adequate cover. Then pour grade beam.

Clearly, #2 is the more conservative option. But my question is, from an engineering perspective, is there anything wrong with option #1? Is there a potential failure mode that could realistically occur from a 45 kip load?

Based on the picture there is more than enough flat area remaining for 3,000 psi concrete to bear a 45 kip load. This does introduce some eccentricity into the pile, but the pile is reinforced to a depth of 15 feet. At that depth I would imagine the eccentricity would be negligible. Is there anything I am missing?

 

[dik]

I'd leave the pile as is and pour the grade beam. Lots of bearing area and I've often cast 16" piles with a single #5 (now, 15M) bar in the centre. Assuming there are no seismic issues or lateral loading.

Used 19'8" bars... rebar came in 18m lengths and lopped them into 3...

Dik

 

[SlideRuleEra]

Agree with Dik, option #1. Just remove any loose concrete with hand tools.

IMHO, option #2 is not conservative, there actually more risk. Cutting the pile off, without rebar damage is not easy. When the cut is made there is real risk that remaining concrete will be fractured.

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[KHoff]

Appreciate the input Dik & SlideRuleEra. I agree.

 

[GC_Hopi]

If you want extra conservatism and punish the contractor a bit for not being careful during the excavation, i am guessing that's what happened, have them add a few circular ties around the pile. This adds a compression ring to the pile which will strength this area. Or so I have been told.

 

[JAE]

I might disagree a bit here - if the pile was a pure wedge shape, would that change your mind?
I can see a chisel point pile top possibly creating problems with the concrete enclosure around it - such as lateral bursting stresses.

You don't quite have a chisel point here but I might have them chip the top down to a more "flat" surface.

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[KHoff]

JAE - I agree that a pure wedge shape (i.e. no flat area for bearing on top of the pile) would be a concern. In that case I think a repair would be required.

I calculated an approximate required bearing area of 27 square inches for the 45 kip load. In this case, there is clearly more than 27 square inches of flat bearing area on the top of that pile.

I just want to be sure there isn't something I am missing here.

 

[EireChch]

Not a structry - but my gut was saying Option 1.

Poor contractor - rebar is a mile off centre and probably insufficient cover on right hand bar.