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April 12,2018 <br /> Page 2 of 5 <br /> Retaining Wall Design <br /> Wall Backfill <br /> All fill placed behind the walls,regardless of whether or not it is in the reinforced backfill <br /> zone, must be compacted as structural fill. The native soils at the site contain a sufficient <br /> enough percentage of fines that will make them difficult,if not impossible, to compact <br /> as structural fill when they are over-optimum in moisture content. Therefore,we <br /> recommend importing a granular soil for use in geogrid reinforced walls that meets the <br /> following gradation requirements: <br /> U. S.Sieve Size Percent Passing <br /> 6 inches 100 <br /> No.4 75 maximum <br /> No.200 5 maximum* <br /> * Based on the 0.25 inch fraction <br /> Imported structural fill should be placed in uniform loose layers not exceeding 10 inches <br /> and compacted to a minimum of 95 percent of the maximum dry density as determined <br /> by American Society for Testing and Materials (ASTM) Test Designation D-1557 (Modified <br /> Proctor). The moisture content of the soil at the time of compaction should be within two <br /> percent of its optimum, as determined by the ASTM standard. <br /> Design Parameters <br /> The following soil parameters were used in our designs: <br /> Soil Type Friction Angle Cohesion Unit Weight <br /> Structural Fill 34 degrees 0 psf 125 pcf <br /> Native Soils 36 degrees 0 psf 125 pcf <br /> psf=pounds per square foot <br /> pcf= pounds per cubic foot <br /> Note:the taller wall sections located near the garage were designed with a 150 psf <br /> dead/live load surcharge as parking is located above the area. <br /> Design Recommendations <br /> The area behind the wall will require excavation prior to block and geogrid placement. <br /> We recommend a maximum 3/4H:1 V temporary excavation behind the wall system <br /> provided the work take place during dry weather and within a several week period. The <br /> cut should be covered with visqueen when grading is not taking place. <br /> The new retaining wall should consist of the Keystone Century-style blocks, or an <br /> equivalent approved by us. The new Keystone Block wall should be constructed as a <br /> Mechanically Stabilized Earth (MSE) wall with segmental block facing.The new retaining <br /> wall should be constructed according to the manufacturers'specifications and the <br /> recommendations provided in this report. <br /> (4 ,21 , <br />