1318 37TH ST 2018-01-02 MF Import

James Pirie JN 97072 March 18, 1997 Page 6 be placed beneath the slab. Additionally, sand should be used in the line -grading process to reduce damage to the vapor barrier, to provide uniform support under the slab, and to reduce shrinkage cracking by improving the concrete curing process. Permanent Foundation and Retaining Walls Retaining walls back911ed on only one side should be designed to resist tF a lateral earth pressures imposed by the soil they retain. The following recommended design parameters are for walls that restrain level backfill: Parameter Design Value Active Earth Pressure' 35 pcf Passive Earth Pressure 350 pcf Coefficient of Friction 0.45 Soil Unit Weight 130 pcf Where: 1. pcf is pounds per cubic foot. 2. Active and passive earth pressures are computed using the equivalent fluid densities. ' For a restrained wall that cannot deflect at least 0.002 times its height, a uniform lateral pressure equal to 10 psf times the height of the wall should be added to the above active equivalent fluid pressure. -4— �= � 2 z The values given above are to be used to design permanent foundation and retaining walls only. The passive pressure given is appropriate for the depth of level, structural fill placed in front of a retaining or foundation wall only. We recommend a safety factor of at least 1.5 for overturning and sliding, when using the above values to design the walls. The design values giver, above do not include the effects of any hydrostatic pressures behind the walls and assume that no surcharge slopes or loads, such as vehicles, will be placed behind the walls. If these conditions exist, those pressures should be added to the above lateral soil pressures. Also, if sloping backfill is desired behind the walls, we will need to be given the wall dimensions and the slope of the backfill in order to provide the appropriate design earth pressures. The surcharge due to traffic loads behind a wall can typically be accounted for by adding a uniform pressure equal to 2 feet multiplied by the above active fluid density. Heavy construction equipment should not be operated behind retaining and foundation walls within a distance equal to the height of a wall, unless the walls are designed for the additional lateral pressures resulting from the equipment. The wall design criteria assume that the backfill will be OEOTECN CONSULTANTS, INC. Q/20