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Re: "Water in the Hole"

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I'm sure you'll get better responses than this, but you may want to reivew
the TxDOT specs for drilled shaft construction and concrete placement
requirements.  I know the FDOT specs deal specifically with this and I
imagine the TxDOT specs do as well.  It serves as an example that the use of
a tremie, etc. is simply the standard of care for this type of construction.

You might also want to ask the geotech if he is willing to put his "just
sink them about three feet deeper" recommendation in writing.

M. David Finley, P.E.
2086 SW Main Boulevard - Suite 111
Lake City, FL  32025
386-752-6400

----- Original Message -----
From: "Bill Polhemus" <bill(--nospam--at)polhemus.cc>
To: <seaint(--nospam--at)seaint.org>
Sent: Monday, July 21, 2003 2:23 PM
Subject: "Water in the Hole"


> I've just returned from an interesting little excursion to inspect some
> drilled-shaft footings being installed on a light-commercial (one-story)
> building project that I designed.
>
> The drilled shafts are there because of the potential for uplift as well
as
> to support the gravity loads of the building. Uplift comes from the
> bodacious expansive soils we deal with here in southeast Texas (and
really,
> over most of the state).
>
> The shafts are 12" and 18" diameter, with bell diameters of 36" and 54"
> respectively. When I arrived they had already poured four of the
thirty-odd
> 12" shafts. They had just informed me prior to my leaving for the site
that
> they had encountered quite a bit of water in the excavations, but "it's
all
> right, we talked to the geotechnical engineer and he asked us just to sink
> them about three feet deeper."
>
> Of course, the result of that is there was A LOT of water in the holes.
The
> foundation contractor seemed to think that since he was doing what the
> geotech told him to do in increasing the shaft depth, that everything was
> hunky-dory.
>
> He was flummoxed when I ordered him to stop placing concrete until we
could
> get a handle on the amount of water. "The geotech told me just to pump
them
> and then we could pour," he complained.
>
> Trouble was that the water was seeping in almost as fast as he could pump.
> As soon as he withdrew the pump, and got his concrete chute in range (yes,
I
> said "concrete chute;" around here, they never heard of a "tremie," and
they
> have no problem dumping the concrete into the excavated hole, even with a
3x
> bell, etc. MEMO TO SELF: Add "must use tremie" to Concrete Notes from now
> on), there was water from one to three feet deep in the excavation again.
>
> My informing him that his placing concrete in standing water was not
> acceptable got the usual
>
"what-the-h*ll-are-you-talking-about-you-*#%@-engineer-we-do-it-this-way-all
> -the-time" rant.
>
> My concern is, first, that placing 4" slump concrete--or just about any
> concrete--into standing water is just inviting the bell to be not worth
@*%#
> when the soil pressure attempts to lift the foundation off the piers. The
> bell is there as much to anchor the foundation as anything else.
>
> Second, that his placing the concrete as he does, from a height, into so
> much water, is going to cause caving and voiding of the concrete to a
> horrific extent.
>
> Of course with the developer standing there, just wanting them to finish,
> I'm pressured to just "let it go," but the developer DOES want to see
> "something in writing" about my concerns.
>
> To me, my concerns are valid even without backup data, but I'm going to
try
> to be dutiful about this. I wonder if anyone here can give me some
pointers
> to info on the net or elsewhere, about placement of concrete in conditions
> similar to these, and the implications thereof.
>
> Thanks.
>
>
>
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