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[SEAOC] Re: [SEAOC] Surcharge on a retaining wall

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If your footings are lightly loaded your 1:1 may work but this can
vary 
considerably depending on whether you are in sand or saturated clay.
Your 
Boussinesq equations can be easily handled by looking at one of the
Tri-Forcess 
Manuals.  In this case get a copy of "Foundations and Earth
Structures" NAVFAC 
DM 7.2 (every engineering office should have one!!).

In there you will find the equations and pressure diagrams already
plotted.  The
numbers are easy to run and the pressure plot gives a good idea of
what is going
on.  There is a specific diagram for a point load "X" distance from a
retaining 
wall of "H" height.

Of major concern will be the backfilling.  You will need to be
careful not to 
put a big vibrating compactor next to your wall.

Of even more importance will be to insure the final grading drains
all water 
away from the wall.  If this is not possible then you will need to
provide 
swales, V-ditches, trenches, buried perforated pipe, etc.  Also look
at the 
other side of the wall and check for weep holes.  If they are absent
or look 
inadequate you may want to drill a few drain holes.

Thomas Hunt


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Subject: [SEAOC] Surcharge on a retaining wall
Author:  seaoc::(SEAOCAB) at ~FABRIK
Date:    5/30/96 12:07 PM


From: seaoc(--nospam--at)power.net
Date: Thu, May 30, 1996 12:07 PM
Subject: [SEAOC] Surcharge on a retaining wall 
To: seaoc
I have recently come across the problem of  putting a spread footing 
behind an existing wall and footing that has little or no capacity
for lateral loading.  The question is how deep to make the new
footing so 
that it does not induce lateral loading on the existing wall footing.
        
Obviously, I could make the footing as deep as the wall footing, 
thereby, eliminating any chance of lateral loading.  However, that 
would require a lot of concrete. Since the new footings are at 
varying distances from the wall,  I would rather make the new 
footings only as deep as necessary.
        
So here's my question...would a 1:1 rule apply? Hypothetically, if I 
had a 10 ft high retaining wall and a surcharge 10 ft away from the 
wall, could I safely assume that there is little or no lateral load 
on the wall?
        
I ask this, because I would like to avoid getting into a Boisenesque 
analysis.  Quick and dirty, is more efficient for this small project.
        
================================================= 
Eric J Scott
escott(--nospam--at)csus.edu
Cline, Agee, and Swedin
Architects and Engineers
=================================================
        
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Subject: [SEAOC]       Surcharge on a retaining wall 
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