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[Towertalk] 'Toes' of a tower concrete base

To: <>
Subject: [Towertalk] 'Toes' of a tower concrete base
Date: Sat, 29 Jun 2002 22:32:24 -0400
Dave et al:

     My responses below.

73 de
Gene Smar  AD3F

-----Original Message-----
From: David Jordan <>
Cc: <>;
<>; <>
To: <>
Date: Saturday, June 29, 2002 9:01 PM
Subject: Re: [Towertalk] 'Toes' of a tower concrete base

>YUP,  It might sink all the way to China!
Nope - just to bedrock or some other, more-dense material that WILL support
the weight.

1997 UBS Volume 2 Table 18-I-A, Allowable Foundation and Lateral Pressure,
shows that clay soil (among others) can be considered to have an allowable
foundation pressure of 1,000 psf.  For a 7X7 = 49sqft foundation, that would
be 49,000 pounds of concrete-plus-structure that could be supported in
clay-like soil.  If there's too much weight, or if it's the wrong type of
soil, then the dirt can't hold it up.

> Please, an extra cubic yard of concrete isn't going to make any
>difference other than  cost him another $85 buck.
Do the math:  5X5X5 = 125 cuft for the basic cube of the foundation.
                        2X7 + 2X5 = 24 cuft for the toe around the perimter
of the foundation
                         Total for engineered design = 149 cuft/27 = 5.52

                       7X7X5 = 245 cuft/27 = 9.07 cuyd for oversized hole.

At ANY concrete price, the larger hole would cost 9.07/5.52 = 1.64 times
more than the proposed, engineered design.  It would also be 1.64 times as
HEAVY as the proposed, engineered design.  Are you SURE that another few
yards of concrete wouldn't hurt?

 The toe for his
>application is useless.  All one has to do is go back and look at the
>instructions for the very same tower published in 1960-70-80...
Maybe the engineers got smarter over the years and changed their design to
reduce costs, making their tower more affordable?

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