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2 <br /> Revised Redi-Rock Retaining Wall Design Western Geotechnical Consultants,Inc <br /> 52XX Glenwood Ave.Property #14 91 2 <br /> Everett,WA <br /> April 17,2015 <br /> Surface Conditions <br /> The property is a moderate to steeply sloping parcel with a level bench where the house will he <br /> sited. The bench appears to be a graded bench. An access drive extends from Glenwood <br /> Avenue up to the building site and there is a steep cut slope along the lower portion of the access <br /> drive. An existing rockery is present along the south end of the cut slope, with exposed soil to <br /> the north of the rockery. The area where the new wall is proposed is mostly exposed till soil on <br /> the slope, with grass and weeds near the bottom and at the base of the cut. <br /> Subsurface Conditions <br /> The site is underlain b glacial till as noted in the cut slope and in the LU! Associates, Inc. <br /> report, The wall will be founded on hard, undisturbed till with a crushed stone leveling course <br /> above. <br /> Stability Analyses(Deep Seated Failure) <br /> We performed stability analyses on the most critical slope section at the location of the proposed <br /> house on the property based on site measurements and the house profile presented in Figure 1. <br /> Both static and seismic loading conditions were analyzed and the seismic analyses utilized a <br /> maximum pseudo-static earthquake load of 0.25 g. For the analyses we assumed the following <br /> engineering properties. <br /> Picket Soils <br /> Unit Weight 120 pcf <br /> Cohesive Strength 50 pcf <br /> Angle of Internal Friction 27 degrees <br /> Rock <br /> Unit Weight 140 pcf <br /> Cohesive Strength .... 950 psf <br /> Angle of Internal Friction 37 degrees <br /> To facilitate our analyses, we used the computer program GSLOPE. The program uses Bishop's <br /> Modified Method of slices and a limiting equilibrium approach to determine the minimum factor <br /> of safety against failure. The program determines the critical failure surface and the resultant <br /> factor of safety tier the slope configuration, soil unit weights and strengths, ground water <br /> location, and seismic loading. The results of the analyses are summarized below. <br /> Loading Conditions Minimum Computed Target Safety <br /> Safety Factor Factor <br /> Static 2.8 1,5 <br /> Dynamic 2.2 1.1 <br /> 2 <br />