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RE: Retaining Wall Surcharge in Snow Country

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Title: RE: Retaining Wall Surcharge in Snow Country


Tom:

It seems to me that the bigger issue in designing retaining walls in freezing climates is groundwater and drainage.  Most retaining walls are designed assuming that the retained soil is fully drained, with weeps or a perforated pipe collection system.  Consequently, the effective soil density is usually on the order of 55-65 pcf.  If the drainage system becomes frozen, and remains so in Spring, it is possible that the retained soil will become fully saturated, and the active earth pressures will double (more-or-less).  Also, before Spring, frost heave could damage the retaining wall.  Both of these effects are potentially more significant than snow surcharge, especially when that surcharge is bearing on frozen soil that will thaw after the snow does.

Our current challenge in Dallas is to keep a very important three-quarter inch sheet of ice frozen in 95 deg. F heat until June 22, or sooner, if the Stars defeat the Sabres in less than 7 games.

Regards,

Stan R. Caldwell, P.E., F.ASCE
Dallas, Texas (Hockeytown South)



Does anyone out there who does snow country design have any opinions on what
to use for a surcharge on retaining walls.  Would you use the ground snow
weight, or some other number.  For example we have tables that say to use
100 psf surcharge for garages and parking areas, and 200 psf surcharges for
highways.  In areas with a 300 psf ground snow weight it seems out of line
to be using this number directly and getting tougher retaining walls then
would be used at a highway.  We'd appreciate any thoughts or recommended
references.

Tom Schaniel
BILL JENKINS ASSOCIATES
Mammoth Lakes, CA