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Re: Retaining/Basement Wall Surcharge

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 Eric-
You might try Figure 11, p. 7.2-74, from Design Manual 7.2 "Foundations and Earth Structures" published by the Naval Facilities Engineering Command.  It presents the Boussinesq formulas for a line load parallel to a wall and a point load next to a wall which should give you an idea of the effect of distance from the wall and with depth. There is a PDF copy of this manual at the following link:
 
 http://www.ce.washington.edu/~geotech/courses/cee523/manuals/NAVFAC72.pdf
 
Regards,
Bill Cain, SE
Berkeley CA
 

-----Original Message-----
From: Eric Ober <eober(--nospam--at)holbertapple.com>
To: seaint(--nospam--at)seaint.org
Sent: Thu, 7 Apr 2005 09:59:57 -0400
Subject: Retaining/Basement Wall Surcharge

This question relates to live load surcharge behind a deep basement (four stories below grade).  We have a fire truck live loading criterion adjacent to the basement wall.  For this load condition, we normally treat the fire truck as an equivalent uniform load of 250 psf.  In basement wall design, the geotechs will normally provide a coefficient which converts the uniform surcharge load into an equivalent uniform horizontal load against the back of the wall.  For our case, where the basement is 40 ft to 50 ft deep, this seems overly conservative for the lowest wall levels, where the surcharge pressure must have dissipated significantly.  Is anyone aware of a published reference which provides some information related to this issue?
 
Thanks.
 
Eric
 
Eric R. Ober, P.E., S.E.
Associate
Holbert Apple Associates, Inc.
3423 Olney-Laytonsville Road
Suite 6
Olney, Maryland  20832
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