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RE: soils pressure

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Joe:

I've been following this thread and what I would suggest is in your assumptions, you need to state that the existing rock is self supporting. If you are willing to do this, then all you need to design the wall and diaphragm for is the free draining material. If you are not willing to make that assumption, then you need to find a Geotech that will. If they won't, the only option, I see, is to design the basement wall for the full lateral pressure.

I am in no way a rock expert, so I would either design the wall for the full pressure or require a Geotech report. That's just me. It all depends on your comfort level.

On a side note, I have a quick question regarding the load path to the floor diaphragm. On a raised floor, I tend to find the controlling issue to be the anchor bolt / mud sill connection. I tend to go with a 4x sill and 24" bolt spacing for the taller walls. Is this what you find? Obviously, you also have to connect the sill to the joists (Simpson A35) and the joists to the sheathing (nailing from above). Just wanted to check if someone was doing something else.

Seth Cutler, EIT
R.L. Morrison Engineering Co.

At 11:27 AM 4/22/2004, you wrote:
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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