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RE: pool wall design
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: pool wall design
- From: "Caldwell, Stan" <scaldwell(--nospam--at)halff.com>
- Date: Thu, 13 Nov 2003 16:34:33 -0600
The way this
is most commonly done in Texas is to core drill one or two holes in the deep
end, and then grout them up prior to refilling the pool. You can probably
forget the idea of adding extra weight ... just calculate the volume of
displaced soil and multiply by 62.4 pcf to see why. Also, if you have
expansive clay soils like we do, draining a pool for any length of time
is risky business even without considering uplift.
Down here, most
pools are free-form gunite and, to be honest, they typically aren't designed by
engineers. I have designed two. The first one cracked due to
shifting soils, leaving a nice 40 ft. ugly dirt collector right up the
centerline. The owner chose not to sue the engineer, since they were one
and the same. My second design is performing better, probably due more
to stable soils than to my design efforts. After 12 years
holding water, the owner (me again) is cautiously optimistic. From this
track record, I would never want to design a pool for any other
Your approach of
designing the shell as cantilevered walls is reasonable, but it would be more
accurate to simply use a 2D computer model with about 20 nodes across a
transverse section. Using a 3D computer model is unwarranted, especially
considering that the design lateral soil pressure will be a
crude approximation at best. That "hardened overcoat" you refer to is
probably just plaster. It is there to keep the water in and to present an
attractive appearance. Plaster is not a structural
material. Use at least 6 in. (preferably 8 in.)
of zero-slump gunite, with plenty of rebar in a
single layer. Insist on chairs to provide 3 in. minimum cover to the
face of the soil, and don't let the contractor substitute bricks or chunks of
... and best regards,
Stan R. Caldwell,
Don't go around saying the world owes you a living.
The world owes you
nothing. It was here first.
.... Mark Twain
it be fair to say list several alternatives to prevent the uplift... say drains,
extra weight, or simply not draining the pool when the soil is saturated?
Obviously different contractors and different sites will demand different
You probably know this but just in case you
don't here's a reminder. One of the most important considerations in pool
design is to accommodate or eliminate uplift due to buoyancy for pool empty -
water table high. Subsurface drains and/or projecting the pool bottom to
enable backfill weight to be included are possible solutions.
H. Daryl Richardson
Pat Clark wrote:
I am looking for
additional references on designing pool walls. We have started by
analyzing these walls as cantilevered retaining wall, but this does not
consider the curvature at the bottom of the pool, and additional hardened
overcoats on the pool walls, etc. Also, any input for my specifications about
leaving pools in a drained conditioned, etc. would be greatly