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Re: Sliding

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Paul, and others

        I would recommend that you specifically AVOID considering soil friction along the side of foundation walls, particularly in the top several (typically 5 to 8) feet of elevation of the wall.  The reason is that variations in the water table level and in short term climatic variables may cause surface soils to swell or shrink to such a degree that they won't even be in contact with the foundation wall let alone be able to transfer frictional shear values.  Below this level you probably could use some value (in the order of 200 to 500 p.s.f.) as a frictional resistance to loading.

        In my view this is not unlike skin friction for piles.  Your geotechnical consultant should be able to put some numbers together for you.


H. Daryl Richardson

Paul Crocker wrote:

     I recently asked a geotechnical engineer on a project about the possibility of having soil friction along the sides of the wall footing, due both to cohesion (like a pile) and friction resulting from the soil pressure on the sides of the footing.  He told me that such forces do exist, but that they aren't particularly significant.  That will probably depend on your soil and the willingness of your geotech to look into it, since it isn't typically considered.     Another approach you can try is to reinforce the slab on grade (if you have one) and use that to spread the sliding force to other parts of the building.  The detailing could be tricky, though, depending on how things are laid out.  You can also look at tie beams that extend out to adjacent columns in line with the wall.  There are quite a few variations and combinations of those concepts. Paul Crocker, P.E.
-----Original Message-----
From: RDAHLMANN(--nospam--at) [mailto:RDAHLMANN(--nospam--at)]
Sent: Wednesday, November 13, 2002 6:40 PM
To: seaint(--nospam--at)
Subject: Sliding
I have a question about sliding in long shear walls. In high seismic regions, sliding can govern footing sizes. Resistance is provided by the friction factor times the dead load weight (times appropriate factors) plus any passive pressure. This can also include return walls.

For long shear walls, it seems like there should be some sort of side friction factor also (similar to caisson skin friction). I have not seen this anywhere, but I would like some input about this possibility.

Richard Dahlmann, P.E.