Limit of skin frictions

[rainandcm]

I am trying to gather information about the maximum unit skin friction for piles.

Prakash and Sharma (1990)suggested fs<=1 tsf. I also read somewhere that fs should stop increasing from 10D~20D depth.

Bowles (1996) only says that fs should be considered but didn't say how.

Coduto (2001) didn't mention limiting fs at all.

Any more reference on this topic?

Thanks.

 

[BigH]

See:

http://www.fellenius.net/papers/171 Critical Depth.pdf

 

[rainandcm]

awesome paper! I've never read this kind of discussion before. Thank you BigH!

 

[Terratek]

If you want more traditional resources that discuss skin friction limits with detph, Das covers skin friction limits in his foundation engineering books. We don't really use piles at all where I practice, so I would revert to Das, rather than the paper BigH recommended if I did have a one-off driven pile project. That doesn't make BigH or that paper wrong, just an approach with a higher comfort level for someone (me) who is not frequently involved in pile design.

 

[ATSE]

BigH correctly sent you to the right source. Fellenius is Dr. Pile, and for the most part "critical depth" idea has gone the way of the dodo bird.
Side friction fs (ultimate) increases with depth, and can be much larger than 1 tsf for CIDH, drill displacement, and driven piles.
In addition to Fellenius, many other texts cover pile capacity, including very common and accessible texts: 1996 Terzahgi-Peck-Mesri, Bowles, Coduto, and NAVFAC 7.2 (to name a few).
All of these provide alpha (su based) and beta (effective stress based) methods to calculate pile capacity.

 

[Panars]

Nothing against Das (I learned from his textbooks) but he is compiling info from other experts in their particular fields. For driven pile, one of the experts Das would be referring to would be Fellenius. I would rate Fellenius over Das as an authority on driven piles, Terratek.

 

[BigH]

As an alternative to Fellenius - Tomlinson's Pile Design and Construction is a great text

 

[Guest262653]

We've been using for years and with good results the LCPC method, developed by Bustamante and Gianeselli, which is directly connected to the CPT test. Regarding skin friction, there is no explicit 'critical depth' concept in the method, just a set of tabulated coefficients relating CPT results and pile unit skin friction. A maximum unit skin friction is also established in this method.

The coefficients have been updated through the years since the initial publishing, but you can get an insight of the method in the following link:

http://www.geologismiki.gr/Documents/CPeT-IT/HTML/lcpc_method.html