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LATERAL EARTH PRESSURE <br /> Basement walls, retaining walls and other walls that retain soil will be subjected to lateral earth <br /> pressure. Cohesive_ (lean clay) lateral earth pressures and parameters must be used in wall <br /> design when cohesive soil acts on walls. Granular soil (sand and gravel) lateral earth pressures <br /> and parameters must be used in wall design when granular soil acts on walls. Estimated lateral <br /> earth pressures and parameters for cohesive and granular soils are given in TABLE L. <br /> _ Active earth pressure design assumes the top of wall moves away from adjoining soil. .Active earth <br /> pressures and parameters must be used in this case. Passive earth pressure design assumes the <br /> top of wall toward adjoining soil. Passive earth pressures and parameters must be used in this <br /> case. If the top wall remains stationary, at-rest earth pressures and parameters must be <br /> considered in design. Increased lateral earth pressure can develop on walls due to poor or <br /> restricted soil water drainage, surcharge loads applied behind walls, over.compacting backfill <br /> against walls and upward sloping ground surfaces behind walls. In these cases higher lateral earth <br /> pressures and parameters must be considered in design of walls. <br /> TABLE L ESTIMATED LATERAL.EARTH PRESSURES as EQUIVALENT FLUID PRESSURE (A) <br /> COHESIVE SOIL GRANULAR SOIL <br /> Approximate total density (pcf) 130 120 <br /> .Approximate friction angle (deg) 15-20 30-35 <br /> - Active pressure coefficient ka 0.5 0.3 <br /> At-rest pressure coefficient ko 0.7 0.5 <br /> Passive pressure coefficient kP 2 3.3 <br /> Active Earth Pressure (pcf) <br /> Drained 65 35 <br /> -- Undrained 95 80 <br /> At-Rest Earth Pressure (pcf) <br /> Drained 90 60 <br /> Undrained 110 90 <br /> Passive Earth Pressure (pcf) <br /> Drained 260 400 <br /> Undrained P 135 190 <br /> Notes: <br /> (A) Excludes cohesive shear strength sliding friction effects <br /> (B) Combined factored soil buoyant unit weight and hydrostatic water head (62.4 pcf) <br /> (C) Excludes hydrostatic water head (62.4 pcf) <br /> Granular backfill should be placed against retaining and foundation walls as a triangular prism with <br /> a 2:1 (horizontal : vertical) slope or flatter as shown in Appendix C (Foundation Wall Backfill and <br /> Drainage Schematic)., Backfill must be free-draining granular material with less than 5 percent <br /> Allied Project 04049 14 July 27, 2004 <br />