Piles going deeper than expected 1

[cbosy]

Does anybody know of any good case studies where piles went significantly deeper than the borings predicted?

 

[slowoldgit]

North Rankin Oil Platform, Australia, see the conf publication (ed Al-Shafei, K.A.)

 

[Mikeki]

Driven piles or bored piles? Suspect driven. Do you want papers for info or to know what is going on. If you want to know whats going on get some dynamic pile testing carried out for pile capacity and hammer performance .

 

[VorpalSword]

Lahad Datu Port in Sabah, Malaysia
Consultants were Posford Duvivier
Main Contractor was Kawasaki Steel (project manager Myoshi, assistant Ichise ) . Posfords (for Sabah Port Authority) argued that the increase in pile length (by about 5-10 metres for 390 piles) was the contractor's problem, Kawasaki proved otherwise, after a major investigation effort including British experts. I don't know if the results of arbitration was ever made public, probably some confidentiality clause.
The general principle appears to be that you cannot contract out risk.

Cheers

 

[Ron]

This happens with reasonable frequency in some karst formations. My experience is that 5-10 percent length variation is typical but have seen 75 percent increase in erratic formations.

 

[BigH]

This is off thread a bit - but in sands if the designer has flubbed it and chosen a non-displacement pile (such as H-pile), the piles can go on "forever". I ran across this on a dolphin project once. H-pile in compact sand. They were having 1 blow per foot!! Did some checks and we chose to do 3 blows/foot or depth based on geotech analyses. Chellis' book has point on this - they put in wedges about 15m up inside flanges to give it some "bearing". This also happened to a very experienced engineer in our outfit long ago -

 

[Focht3]

BigH:
I'll conditionally disagree regarding "non-displacement" piles going on "forever." In my experience, this doesn't happen in "clean" silica sands with D_R in excess of about 80 to 90 percent. I know that's pretty "dense" - but also fairly common in areas with OC soils.

The "forever" phenomenon can occur in soils with D_R of less than 60 percent, though.

 

[BigH]

Focht3 - good to see you back! You understand the " "!! Of course, in our cases we didn'have OC sands - the point is that in loose to low compact sands, non-displacement H-piles might not be the most appropriate choice; in denser strata, okay.

Best regards.

 

[Mikeki]

Further thoughts on driving piles into granular soils....

Quite often driving piles to "set" in granular soils can lead to longer than necessary piles. Rather than just keep driving piles deeper and deeper chasing a "set" why not stop at the design depth and record the blow count. Then carry out dynamic testing and CAPWAP analysis to find out what shaft friction and end bearing the pile has. If the pile test show the pile to have the required load then drive remaining piles to the blow count recorded for the test pile. Then carry out a bit more testing (say 5 to 10%) during installation of the remaining piles.

A properly engineered job with a bit of Quality Control as well, every one should be happy, including the insurance company.

Happy pile driving to everyone.

 

[philhelf]

I had a INDOT project driving piling for a CSX railroad bridge and the H12 x 53 piling went deeper (30' total) that planned.(20') Of course we were paid by the foot so no loss to us. The aluvial soil did not give the friction needed. Whenever possible we always drove the piling to refusal. (OK by the engineer)

The resident engineer, with approval from design, switched to 14" tube piles with a 1 inch plate on the bottom. The piles then went less than designed depth, but still achieved desired bearing.

 

[dch337]

hatrack-

I'm surprised INDOT specified H piles in a non-end bearing situtation. They almost always dictate SEC piles in that case....