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Re: Foundation on Expansive Clay

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Fountain,
Depends on how expansive the clay is. Presaturation of the soils is also
recommended along with deepened edges. The depth of presaturation can vary
from 12 to 24 inches, the deepened edge from 12 to 24 inches. The idea is to
keep the moisture content consistent within and below the slab. Care should
also be taken with any potential conduit,  such as utilities. Since you have
"light" confining pressures it (expansive soil) is even more critical being
addressed.
Chris Lillback P.E.
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----- Original Message -----
From: "Fountain Conner" <fconner(--nospam--at)pcola.gulf.net>
To: <seaint(--nospam--at)seaint.org>
Sent: Wednesday, April 04, 2001 4:05 AM
Subject: Foundation on Expansive Clay


>
> I need to put some lightly-loaded foundations on clay "with the potential
> for expansion".
>
> These foundations will carry a bark blowline in a paper mill.
>
> If all were normal these foundations would be 7 feet long x 8 feet wide x
3
> feet thick.  They each would have a vertical pipe 20 feet tall, carrying a
> horizontal blowline.  Maximum soil pressure (max load and wind) would be
> about 2000 psf.  Static maximum load is about 650 psf.  The geotechnical
> report allows at least 2500 psf, plus 25 percent for short-term live load
> (like wind).
>
> Plain vanilla...  Until I factor in the potentially expansive soil.
>
> My thinking is to turn down the outside edge of the footing an additional
6
> inches.  If this clay is expansive, it shouldn't be given to capillary
> action, and will provide a seal, preventing the soil beneath the
foundation
> from seeing the varying moisture content.
>
> What do you think?
>
> Item 2:
>
> I had intended to place each "mast" in a sleeve, plumb it and grout it
> into position -- cheap, but effective.  I *can* put a mast on a large,
> thick
> baseplate, and perch it on nuts below the base plate, with double nuts
> above.  If I do this, I can allow enough room below the lower nuts to
> adjust each mast plumb if there is some movement.  I'm hoping you guys can
> convince me that this step is overkill.
>
> Ideas?
>
> Thanx,
>
> Fountain E. Conner, P.E.
> Gulf Breeze, Fl. 32561
>    Phone 850-932-5547
>    Fax      850-934-1916
>
>
>
>
>