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Re: Foundation Underpinning

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I suggest that you specify that the excavation be done in sections about
5 ft., then skip 5 ft., then exc. 5 ft., etc. Then when the new wall is
installed in Phase A, the remaining sections can be excavated and the
remaining wall installed.

Stan Scholl, P.E.
Laguna Beach, CA

On Fri, 23 Nov 2001 12:33:42 -0600 "Jason Kilgore" <jkilgore(--nospam--at)leok.com>
writes:
> I have a job where the architect wants to add a lower level to a 
> structure,
> and he wants the lower area to be the same as the upper area.
> 
> At the exterior wall, I think this is possible.  Excavate both sides 
> of the
> wall, then when you get to the foundation, install a 
> needle-beam/column
> system to "unload" the wall (a column or drilled pier on each side 
> of the
> wall with a beam punched through).  Continue excavating under the 
> footing,
> pour a new footing and wall, then you're done.
> 
> Unfortunately, in several locations, there is no access on the 
> opposite side
> of the wall from the new lower level (one locations has a very 
> crowded
> mechanical room opposite).  I can't think of a way to excavate 
> directly
> under the existing footing.
> 
> These interior walls are fairly lightly loaded (mostly the weight 
> from tall
> interior CMU walls, but no "structure" weight or live load).  The 
> largest
> excavation is 7'-0" from bottom of existing footing to finished 
> floor.
> 
> One solution I have proposed to the architect is by Atlas systems, 
> Inc.  It
> uses a combination of steel resistance piers and helical soil-nails 
> to
> underpin an existing foundation, but the lower wall is offset the 
> width of
> the wall + 4" (16" offset for a 12" wall).  He wasn't happy about 
> loosing
> 16", and in one location he really can't loose 16".
> 
> Does anyone out there have any suggestions?
> 
> ----
> Jason W. Kilgore, P.E.
> Leigh & O'Kane, L.L.C.
> jkilgore(--nospam--at)leok.com
> (816) 444-3144
> 
> 
> 
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