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Thomas Kelly JN 95192 <br /> June 7, 1995 Page 5 <br /> depends on the slab shape and the amount of steel placed in it. Reducing the wate; to <br /> cement ratio of the concrete and curing the concrete, by preventing the evaporation of free <br /> water until cement hydration occurs,will also reduce shrinkage cracking. <br /> P@fIR�0QJ1t_EoUpdaLio���d.Retai�ing Wal(s <br /> Retaining walls backtilled on only one side should be designed to resist thE lateral earth <br /> pressures imposed by the soils they retain. The following recommended design parameters <br /> are for walls less than 12 feet in height that restrain level backfill: <br /> P�Ltlmeter _ _- _Desj9n Value <br /> Active Earth Pressure* 30 pcf <br /> Passive Earth Pressure 350 pcf <br /> Coefficient of Friction 0.40 <br /> Soil Unit Weight 120 pcf <br /> Where: <br /> (1) pci Is pounds per cubic foot. <br /> (?.) Active and passive earth pressures are <br /> computed using the equivalent fluid densities. <br /> * For restrained walls that cannot deflect at least <br /> 0.002 times their he?yht, a uniform laterr,! <br /> pressure of 100 psf �hould 6e added to the <br /> above active equivalent fluid pressure. <br /> The values given above are to be used to design permanent foundation and ratalning walls <br /> only. We recorrmend a safety factor of at least 1.5 for overturning and slfding, when using <br /> the above recommended values to design walls. <br /> The design values given above do not include the effects of any t�;�drostatic pressures <br /> behind the walls and assume tha; no surcharge slopes or loads, such as vehicles, will be <br /> placed behind the walls. If these conditions exist, those pressures should be added to !he <br /> above lateral soil pressures. Also, if sloping backfill is desired behind the walls, we will need <br /> to be given the wall dimensions and the slope of the backfill in order to provide the <br /> appropriate design earth pressures. <br /> Heavy construction equipment should not be operated behind retaining a7d foundation <br /> walls within a distance equal to the height of �� wall, unless the walls are designed for the <br /> additional lateral pressures resulting from the equipment. The compactio,i of backfill near <br /> GIiOl7iC11 CONSUI:Ii�N9ti,INC <br />