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G & M Investments <br />November 11, 1993 <br />P-316I <br />Page 7 <br />vapor barrier and to provide uniform support under the slab. <br />Use of sand over the vapor barrier also provides more even <br />curing of ttie slab, resulting in less shrinlcage cracking. <br />PERNANENT !•OUNDATION AND RETAINING WALLS <br />Retaining oz foundation walls backfilled on one side only <br />ehould be deszgned to resis', lateral earth pressures imposed <br />by the soils reta.ined by these struct,res. The following <br />recommended design parameters are for walls less than twelve <br />(12) feet in height which restrain level backfi7.1: <br />Design <br />Parameter _ Value <br />Active Earth Pressure* <br />Pasaive Earth Pressure <br />Coefficient of Friction <br />Soil Unit Weight <br />35 pcf <br />350 pcf <br />0.4 <br />125 pcf <br />Where: <br />1) Pcf is oounds per cubic foot <br />2) Active and passive earth pressures are <br />computed using equivalent the fluid <br />densities. <br />For restrained walls which cannot deflect at <br />least 0.002 times the wall heiaht, a uniform <br />lateral pressure of one hv�..:ed (100) psf <br />should be added to the ac�ive equivalent <br />fluid pressure. <br />The values given above are to be used for desiyn of permanent <br />founriation and retaining walls only. An appropriate eafety <br />factor ahould be applied when designing the walls. We <br />recommend using a factor of safety of at least 1.5 for <br />overturning and sliding. <br />The above design values do not include the effects of any <br />hydroatatic pressures behind the walls and asaume that no <br />surcharge slopes or loads will be placed above the walls. If <br />these conditions exist, then those pressures should be added <br />to the above lateral pressures. Also, if sloping backfill is <br />GEOTECY, CONSULTANT�, INC. <br />