Piles not imposing stress/load on surrounding soil

[Catjacob]

Three weeks ago, I read a trade newspaper which reported a foundation contractor put some kind of steel sleeve over the top, say 6m, of the bore piles so that the pile would not impose any stress on the top layer of soil. Unfortunately, I can’t remember what it is now.....

Dose anybody know more about it???

 

[PSlem]

http://www.foundationtechnologies.com/showitem.php?pid=4

 

[rochplayer]

It sounds more like isolation casings to me. Basically a double casing - an interior casing filled with concrete and rebar that takes the load from the structure and an exterior casing that is larger providing 3 or so inches clear space to allow pile lateral movement, or less if only axial isolation is required. I've used them to protect substandard existing retaining walls from new foundations for bridge widenings.

 

[DRC1]

I have seen casings used as you describe for test piles to isolate the friction from soil that will be removed in the course of the work.