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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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Subject:
Inadequate Construction Control 