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Author:
R. Liau
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2002-05-14 |
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I need the help of some experts please.
Situation:
- Bored piles with diameter of 2m and deepth of 60m;
- Shaft bearing (friction piles) only;
- Piles in groups (4-6 piles);
- Ultimate Capacity: 15000 kN
- No battered piles allowed.
Environment:
- silty sands to sandy silts, locally clay;
- local subsidence;
- earthquake considerations (liquefaction, settlement);
- Groundwater table: 2-5m below surface.
Construction:
- reversed circulation;
- slurry used;
During construction the pile head (pile cut-off) was not adequately checked from site supervision. Concerns over the following items remain:
- Inadequate (locally no) concrete cover to reinforcement (ca.3%) and/or poor quality concrete close to pile head (upper 1-5m) outside the rebar cage.
- Construction joints pile head to pile cap are not cleaned/prepared adequately.
Questions:
A) How could the pile group behave (- considering inadequate construction methods applied-) during large lateral forces/moments e.g induced by earthquakes (Magnitude is up to 7) ?
B) What affect have the defective pile(s) in compression, what in tension ? (Lack of concrete outside the reinforcement cage)
C) What affect has a potential liquefaction in the level of pile head - pile cap ? (I guess rotation - but to what significance?)
D) Long-term durability consoiderations ?
E) What possibilities do I have in order to proof - in case of doubts - that there are no defects around the pile head (after the pile cap is casted) ? Sonic tests just give information within the rebar-cage. Any other methods ? Or is the problem not significant enough (except the durability concern) ?
Thanks for your kind effort and help. I appreciate it.
Liau
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Follow-up:
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Author:
Anton
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2002-07-01 |
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you can core the concrete from the top of the pile and test retrived samples. This is standard practice to check concrete quality even of the entire pile length.
Do not even think about the effects of bad concrete with regards to pile performance, just test the concrete and take out the all bad concrete if there are any.
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Follow-ups:
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Subject:
Inadequate Construction Control 