] [Thread] [Date] [Author]

["Bruce Holcomb" <bholcomb(--nospam--at)brpae.com>]

I am working on a design for a project in Texas for which we are considering a PT slab above grade 10" - 12"... haven't decided yet if this is a good approach, but wanted to ask if that may be a reasonable approach for your design?  The answer will depend on several variables, including the spacing of the APG piles.  The reason we may use a PT slab is the same as your case... expansive soils.

Our site appears to have only slightly expansive soil... we may end up over-excavating 2'-3' and replacing with select structural fill to reduce swell potential.

Bruce D. Holcomb, PE
Butler, Rosenbury & Partners
300 S. Jefferson, Suite 505
Springfield, MO 65806-2217
ph (417) 865-6100
fax (417) 865-6102


   

-----Original Message-----
From: Michael Hemstad [mailto:mlhemstad(--nospam--at)yahoo.com]
Sent: Wednesday, June 04, 2003 1:31 PM
To: seaint(--nospam--at)seaint.org
Subject: augered piles


I have a project in Texas with a large concrete slab
supported on auger-cast piling, lots of them, going
down about 25 feet to limestone.  Due to expansive
clays, I have potential uplift.  I am resisting this,
or trying to, using a high-strength (Dywidag or
Williams) threadbar drilled and grouted into the
underlying rock.  To install these, a plugged pipe
(about 4 inch diameter) will be pushed down the middle
of the pile before the grout sets.  Then, a few days
later, the driller will drop a rock drill down the
pipe and drill down into the rock.  The bar will be
dropped in and grouted full length.

My question is, should I take the opportunity to
pretension this bar?  The potential uplift is a good
deal more than the dead load, and probably greater
than the tension capacity of the grout.  It means
two-stage grouting of the bar, and the cost of the
jacking, so it's not free, but not too expensive.  Any
opinions?

Thanks,
Mike Hemstad
TKDA
St. Paul, Minnesota

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