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RE: Downdrag on cast in place drilled piers (caissons)

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Yes.  But it is more commonly done through highly expansive upper soil stratas in order to avoid uplift on the caisson.  The hole is drilled and a bentonite slurry is placed between the caisson and the soil.  It provides bracing of the caisson laterally, but will not provide a surface for uplift.  Expansive soil volumes vary seasonally with moisture content.  As the expansive strata expands, the slurry is squeezed out at the top into a reservoir, and as the soil shrinks the slurry fills the void space again.  And if there is any caving, the coefficient of friction is almost nothing. 

Harold O. Sprague

-----Original Message-----
From: Mark Baker [mailto:shake4bake(--nospam--at)]
Monday, September 22, 2003 1:13 PM
Subject: Downdrag on cast in place drilled piers (caissons)


Has anyone had any experience with the installation of a sleeve throughout the fill depth in contact with a caisson to eliminate the effect of downdrag on the caisson shaft.


I am entertaining the idea of a 24" dia. pvc pipe sleeve, have for now ruled out the use of sonotube.




Mark D. Baker