PIle Group Densification
PIle Group Densification
(OP)
We are consultants for a pile driving project where contractor is driving 100 feet long piles in dense sands. Pile caps have usually 8 to 12 piles in it. How do I find out it Pile group densification is happening. some of the pile caps have uneven embedment of piles within the pile cap. Even though the contractor is driving piles radially outwards, piles driven later in the pile group are sticking 10-15 ft above the initially driven piles within the same group. I would really appreciate any suggestions.
thanks
thanks





RE: PIle Group Densification
BTW: What type of piles are being driven? H-Piles, Pipe piles, etc.
RE: PIle Group Densification
I just returned from the DFI Conference in Chicago. A paper was presented there by Emre Beringen, a Ph.D. candidate at the University of Wisconsin-Madison on the stiffening effect of driven piles. His research suggests that there is a significant stiffening effect out to 8-10 pile diameters.
If you wanted to measure the amount of densification you could perform before and after CPT probes.
If your contractor is meeting the refusal criteria with shorter and shorter lengths of pile, then you almost certainly have densification happening, although other explanations are certainly possible.
I suspect that you are driving tapered or pipe piles. I would also suspect that the effect might be less pronounced with H-piles.
The case history presented in Appendix C of USACE EM 1110-2-2906 might be helpful to you in this instance. You should contact DFI or Mr. Beringen directly if you wish to obtain a copy of the paper recently presented in Chicago.
Good luck!
Jeff
Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com
RE: PIle Group Densification
thanks jeff, I will contact Mr. Beringen to see if I can get a copy of that paper.
thanks
kapil
RE: PIle Group Densification
Also check out the case history in the USACE manual. The fact that you are getting early refusal could be due to denser soils that were not adequately defined during the site investigation. Depending on your response (i.e. cut off at finished elev, pull out and redrive, or let sit and restrike, etc.) you may want to amend your load test program.
Jeff
Jeffrey T. Donville, PE
TTL Associates, Inc.
www.ttlassoc.com
RE: PIle Group Densification
The following might help in more detail.
ht
RE: PIle Group Densification
RE: PIle Group Densification