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Re: Retaining wall design pressures

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In a message dated 8/28/98 1:07:33 PM Pacific Daylight Time, wellive(--nospam--at)ibm.net
writes:

<< What are opinions regarding retaining wall design pressures when the
 backfill material is completely saturated i.e. water table up to the
 ground surface.
 
 Would the full active equivalent fluid pressure of the soil be additive
 with a full hydrostatic design pressure??
 
 Barry H. Welliver
 wellive(--nospam--at)ibm.net >>

Just completed a similar project where the wall was supporting a stormwater
detention pond.

You need to apply the full active pressure (equal to gamma bouyant x Ka) plus
hydrostatic pressure.  You will also need to consider the hydrostatic pressure
upward on the underside of the footing (which can vary greatly).  For example
if you build on an impervious surface (setting on rock) you could conceivably
have no hydrostatic uplift.  If you build on some permeable subgrade the
pressure distribution has to be determined by creating a flow net.  

I'm not sure about all of the available retaining wall software but to the
best of my knowledge, some very popular packages neglect this uplift. 

Ron Roberts