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RE: Active, At-Rest, Passive Soil Pressure

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FYI, Caltrans uses 100% of vertical pressure (i.e.
K=1) as lateral pressure for box culvert design [BDP
6-8], considering soil unit weight of 140 pcf.


--- "Sherman, William" <ShermanWC(--nospam--at)cdm.com> wrote:
> I typically assume k=0.50 for the at-rest lateral
> pressure coefficient for
> granular soils, unless otherwise provided by the
> geotech engineer. Thus, for
> a granular soil with a saturated unit weight of 125
> pcf and with hydrostatic
> pressure: 
> 
> 0.5(125-62.4) + 62.4 = 93.7 pcf
> 
> For clays, I've been told that the lateral soil
> pressure coefficient can be
> as high as k=1.0 for at-rest conditions. I typically
> ask the geotechnical
> engineer to provide at-rest earth pressures, as well
> as active and passive
> earth pressures.   
> 
> 
> -----Original Message-----
> From: Jeff Smith [mailto:smthengr(--nospam--at)sirius.com]
> Sent: Wednesday, August 22, 2001 5:51 PM
> To: seaint(--nospam--at)seaint.org
> Subject: RE: Active, At-Rest, Passive Soil Pressure
> 
> 
> 
> |~|However, at-rest pressure is now codified in the
> 2000 IBC, which
> |~|does a much
> |~|better job with basement walls and retaining
> walls than the UBC did.  IBC
> |~|Table 1610.1 gives prescriptive active pressure
> values for USCS
> |~|soil types
> |~|and indicates to use 60 pcf for granular soils on
> walls
> |~|restrained by rigid
> |~|floors [at-rest pressure] and 100 pcf for
> silt-clay on restrained walls.
> |~|Further it indicates wood joist floors are not
> considered rigid.
> 
> What would be the highest pcf force on a restrained
> retaining wall with no
> drainage to relieve hydro static pressure, assuming
> no surcharge forces and
> level backfill?
> 
> Jeff
> 
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