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Re: Passive soil pressure in granular soils

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For such a soil, an angle of internal friction Phi=30deg seems to be a reasonably conservative estimate (see Bowles, Foundation Analysis and Design, Table 3-4, p.163).
In tis case a Kp not greater than 3.00 and a mu=coefficient of soil-to-concrete (supposed to be poured directly on that soil) not greater than tan30=0.577 could be acceptable values, at least for preliminary design purposes.
I, personally, would suggest a 20% reduction of mu, to take into account the possibility of locally ecountering more fines.
Stathis Papageorgiou
Athens, Greece      
----- Original Message -----
To: Seaint
Sent: Saturday, March 29, 2003 8:57 PM
Subject: Passive soil pressure in granular soils

I am working on a project in the Spokane, WA area.  The soils report indicates the material at the base of the footing is silty gravel with sand, medium to coarse grained, N=25, ASTM D2487=GM, no water.  I need to do some preliminary design on the footing this weekend.  What would be a conservative value to use for passive pressure coefficient (Kp) and for  soil-to-concrete friction?  Thanks in advance for your help.


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