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RE: soils pressure

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Rand,

If you're talking about vertical, or gravity, pressures, you're right.

But when you consider lateral pressures, then no.  In soils, the assumption
is that the parabolic failure plane extends from the bottom of wall to the
free surface.  If that failure plane is interrupted, then the lateral load
is reduced.

Water exerts the same pressure in all directions because it has little
internal friction.  Not so in soils.

JPRiley
------------



Doesn't a 1" diameter of water 12' tall exert the same pressure as a 1 foot
diameter column? Isn't it the same for soil? doesn't a 12' tall column of
soil exert the same pressure if it's 2' thick or 10' thick column?

Lateral pressures are usually based on the cubic foot weight of soil never
does the distance behind the wall get factored in (except Caquat forces
etc.) so I think so-called "full" soil pressure would be present as long as
loose (then compacted) fill is loaded behind the wall. Use the rock as your
wall attach a ledger for your floor then you have an economic solution that
your "friends" will be happy with.
Engineering is an art in that when you can bring along the reluctant to do
the right thing it means so much more than just the design alone.

My thoughts,
Rand



----- Original Message -----
From: "Jesus Gomez" <jgomez(--nospam--at)schnabel-eng.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Friday, April 23, 2004 8:04 AM
Subject: FW: soils pressure


Joe,

As indicated previously, the earth pressure is dependent on the width of
drainage material between the rock face and the wall. A small width (1 to 3
ft), will reduce the pressures significantly. Your assumption of full soil
pressure is very conservative (assuming there is no water and that there are
no rock pressures).

Jesús Gómez, Ph.D., P.E.
Associate
Schnabel Engineering
510 East Gay Street
West Chester, PA 19380
jgomez(--nospam--at)schnabel-eng.com

>
> -----Original Message-----
> From: Joe Grill [mailto:jgrill(--nospam--at)swiaz.com]
> Sent: Thursday, April 22, 2004 12:27 PM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: soils pressure
>
>
> O.K. guys, one more time, I did design the wall for full soil pressures,
> and once again (in one of my posts) what I used was confirmed by a
> geotech.  The contractor and architect were trying to tell me there
> wouldn't be any soil pressure due to the vertical cut in close proximity
> to the wall.  The vertical cut is not soil, rock rubble, rock with soil
> or even large boulders, it is a vertical rock face... solid rock. J.
> Grill
>
> -----Original Message-----
> From: Bill Allen [mailto:T.W.Allen(--nospam--at)cox.net]
> Sent: Thursday, April 22, 2004 10:58 AM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: soils pressure
>
> Thanks, Paul.
>
> I was hoping someone would say out loud what I was thinking.
>
> T. William (Bill) Allen, S.E. (CA #2607)
> ALLEN DESIGNS (http://www.AllenDesigns.com)
> San Juan Capistrano, CA
>
> :-----Original Message-----
> :From: Paul Feather [mailto:pfeather(--nospam--at)SE-Solutions.net]
> :Sent: Thursday, April 22, 2004 10:08 AM
> :To: seaint(--nospam--at)seaint.org
> :Subject: Re: soils pressure
> :
> :Joe,
> :
> :I would not design a 12 foot retaining wall without a soils report. I
> do :not :see how you can assume anything less than full soil pressure
> occurring at :some point in the life of the structure.  Anything less is
> opening yourself :up to all kinds of potential problems and liability.
> Soil moves and shifts :with time and changes in moisture content, the
> cut will not stand :indefinitely.  Also, who is liable when the near
> vertical cut does not hold :and kills one of the construction workers?
> :
> :
> :Paul Feather PE, SE
> :pfeather(--nospam--at)SE-Solutions.net
> :www.SE-Solutions.net
> :----- Original Message -----
> :From: "Joe Grill" <jgrill(--nospam--at)swiaz.com>
> :To: <seaint(--nospam--at)seaint.org>
> :Sent: Wednesday, April 21, 2004 3:00 PM
> :Subject: soils pressure
> :
> :
> :> I have been asked to design a basement wall with a 12' retained
> height of :> soil.  There has been no geotechnical review of the
> residence, but the :> architect, who has done other work in the area,
> tells me the cut will :> probably stand almost vertical.  If this near
> vertical face is just a :couple :> of feet away from the wall and the
> backfill is a free draining fill, will :> the fill be able to achieve
> full lateral soil pressure against the wall. :> The
> architect/contractor/owner wants to use the floor diaphragm to :restrain
> :> the top of the wall.  If the full lateral soil pressure is achieved
> then :the :> diaphragm doesn't have the capacity to restrain the wall.
> I have :suggested :> a geotech be brought in to look at the excavation
> and make :recommendations :> at that point, but of course that hasn't
> been received very well.  If the :> full soil pressure is not activated
> will there be any pressure at all and :> how is it calculated. :> :> Any
> ideas? :> :> Joseph R. Grill :> :> :> ******* ****** ******* ********
> ******* ******* ******* ***
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