Return to index: [Subject] [Thread] [Date] [Author]

RE: Foundation on Expansive Clay

[Subject Prev][Subject Next][Thread Prev][Thread Next]
I used to justify it by making the pile cap a little bit "thinner" than the
usual h*ll-for-stout bearing mat-type footing. As I said, you can
undoubtedly use a 24-inch cap with your drilled shafts, and it will work
fine.

We usually use the REALLY THICK mat footings so we don't have to bother with
a flexible bearing foundation. But with the Drilled Piers, the point is
moot.

William L. Polhemus, Jr., P.E.
Polhemus Engineering Company
Katy, Texas
Phone 281-492-2251
Fax 281-492-8203


-----Original Message-----
From: Fountain Conner [mailto:fconner(--nospam--at)pcola.gulf.net]
Sent: Wednesday, April 04, 2001 2:56 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Foundation on Expansive Clay


You missed the point.  These are isolated yard footings, spaced some 60
feet apart.  I can stand some vertical displacement +/- as much as 6 inches
wouldn't hurt a bit.

Spread footings calculate to 7 ft x 8 ft.  I can stand as much as 1/2
differential vertical displacement across the footing.

Bill P suggested drilled footings.  I looked at that first, and didn't like
the way it was shaping up.  It's looking better all the time.

Fountain

----------
> From: Greg Smith <strusup(--nospam--at)gte.net>
> To: seaint(--nospam--at)seaint.org
> Subject: Re: Foundation on Expansive Clay
> Date: Wednesday, April 04, 2001 2:06 PM
>
>      It seem's to me that the WHOLE structure will need treating because
if
> you simply stabilize the colums and footings and the clay lifts the rest
of
> the building then that is the same as the columns settling.
>      Maybe piers and grade beam with degradable (cardboard) forms under
the
> gradebeams - and/or - consolidate the site (calcium).  Also post
tensioning
> as a suggestion.
>
> Greg
>
> ----- Original Message -----
> From: "Fountain Conner" <fconner(--nospam--at)pcola.gulf.net>
> To: <seaint(--nospam--at)seaint.org>
> Sent: Wednesday, April 04, 2001 12:01 PM
> Subject: Re: Foundation on Expansive Clay
>
>
> > Unfortunately, it appears that these expansive clays extend to China.
> >
> > 1.  What would a couple feet of undercut and backfill gain me?
> >
> > 2.  How likely am I to get differential movement in excess of 1/2" in a
> > yard foundation 7ft x 8ft?
> >
> > Fountain
> >
> > ----------
> > > From: Bill Polhemus <bill(--nospam--at)polhemus.cc>
> > > To: seaint(--nospam--at)seaint.org
> > > Subject: RE: Foundation on Expansive Clay
> > > Date: Wednesday, April 04, 2001 11:02 AM
> > >
> > > Oops, I didn't catch that (I'm used to an active zone of 10 ft or so
> here
> > in
> > > Southeast Texas).
> > >
> > > You're right, John. If it's only a 6 inch active zone, excavating it
out
> > is
> > > the best alternative. In fact, I'd recommend doing that up to about 5
or
> > 6
> > > feet or so. After that, it's worth looking at a cost comparison.
> > >
> > > William L. Polhemus, Jr., P.E.
> > > Polhemus Engineering Company
> > > Katy, Texas
> > > Phone 281-492-2251
> > > Fax 281-492-8203
> > >
> > >
> > > -----Original Message-----
> > > From: John P. Riley [mailto:jpriley485(--nospam--at)peoplepc.com]
> > > Sent: Wednesday, April 04, 2001 9:55 AM
> > > To: seaint(--nospam--at)seaint.org
> > > Subject: Re: Foundation on Expansive Clay
> > >
> > >
> > > "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."
> > >
> > > Is the expansive clay layer only 6" thick?  If this "turn-down"
method
> is
> > > effective in protecting the soil within the 6" zone, what about the
soil
> > > beneath IT?
> > >
> > > My first inclination is to overexcavate and backfill.
> > > __________________
> > > John P. Riley, PE, SE
> > > Riley Engineering
> > > 20 Oakwood Drive, Blue Grass, Iowa 52726
> > > Tel & Fax:  319-381-3949
> > > jpriley485(--nospam--at)peoplepc.com
> >