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• Lateral Earth Pressure (pcf) <br />Active Passive At-Rest <br />Site Clayey Soils 60 250 80 <br />Granular Soils (<35% fines) 45 320 65 <br />The equivalent fluid unit weights given above apply only to walls with level or gently <br />sloping backfills. If steep upward sloping backfill is needed, then we should be advised <br />and appropriate equivalent fluid units weight should developed for the specific backfill <br />slope. <br />(2) Bacld-ill should be placed in uniform lifts and compacted to between 88 to 92% of [he <br />maximum dry density as determined by ASTM D1557 at a moisture content near <br />• optimum. Care should be taken not to overcompact the backfill since this could cause <br />excessive lateral pressure on the walls. <br />(3) All retaining walls should be provided with adequate drainage so that hydrostatic pressure <br />will not build up behind the wall. <br />(4) The coefficient of friction for sliding for concrete footings of slabs on cohesionless soil <br />(< 35 percent fines) can be taken to be 0.45. Base cohesion of 500 psf can be used for <br />lateral load calculations for footings on cohesive (clay) soils. <br />(5) The reclaim tunnel should be placed on afree-draining bedding material, which should <br />extend up to the springline. The bedding should be provided with an outfall so that <br />' collected water will be eliminated. <br />' 27 <br />