ITEM 23 ATTACHMENT 6 - Project Plans

December 21, 2022 Job No. 4031.101 Page 9 BERLOGAR STEVENS & ASSOCIATES RETAINING WALLS Retaining walls can be of conventional cantilever or gravity type. The following geotechnical criteria should be used for the retaining wall designs: 7.11.1. Lateral Earth pressures Backfill soils for cantilever-type concrete or masonry walls should have a PI of 20 or less for soil placed within 5 feet of the wall. The following are our recommended lateral earth pressures for retaining walls: Active Equivalent Fluid Pressure (Level backfill and drained conditions) 55 pcf Active Equivalent Fluid Pressure (3H:1V backfill and drained conditions) 65 pcf Active Equivalent Fluid Pressure (2H:1V backfill and drained conditions) 100 pcf At-Rest Equivalent Fluid Pressure (Level backfill and drained conditions) 80 pcf Seismic Equivalent Fluid Pressure – Walls Retaining More than 6 Feet (in addition to active equivalent fluid pressure, SEAOC 2010 1) 80 pcf Surcharge Load, where applicable Designated by structural engineer For terraced walls, the lower wall should be designed to support the backfill and the load from upper wall. For the walls retaining more than 6 feet, the total pressure computed would act on the wall as the same location as the initial static pressure; i.e., the resultant would act at a height of H/3 above the base. 7.11.2. Retaining Wall Foundations Conventional retaining walls can be supported on shallow foundations. The following may be used to design the retaining wall foundations: Allowable Bearing Capacity (DL + LL) (may be increased by one-third for seismic and wind loads at the discretion of the structural engineer) 2,500 psf Allowable Passive Equivalent Fluid Pressure (neglect the upper 2 feet) * 350 pcf Allowable Base Friction Coefficient * 0.25 Minimum Footing Depth 2 feet * no reduction is required when combining passive resistance and friction 1 SEOC 2010 Convention Proceedings, 2010. Seismic Earth Pressures on Deep Building Basements.