1901-1919 N Fairview St - Soils Report

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603284-001 5.4 Lateral Earth Pressures Recommended lateral earth pressures are provided as equivalent fluid unit weights, in psf/ft. or pcf., for retaining walls in drained conditions using onsite sandy soils as backfill. These values do not contain an appreciable factor of safety, so the structural engineer should apply the applicable factors of safety and/or load factors during design. TABLE 4: LATERAL EARTH PRESSURES Condition Active At-Rest Passive Coefficient of Friction Equivalent Fluid Unit Weight with Granular Backfill (psf/ft.) Level Backfill,Level Backfill, Static Condition Seismic Increment 40 psf/ft 20 psf 65 psf 20 psf 300 - 0.35 - Walls that are free to rotate or deflect may be designed using active earth pressure. For the basement walls or walls that are fixed against rotation, the at- rest pressure should be used. The seismic increment of earth pressure should be distributed as an inverted triangular distribution and the dynamic thrust should be applied at a height of 0.6H above the base of the wall. Care should be taken to provide appropriate drainage so as no water is allowed to remain behind the retaining wall for any significant length of time. Retaining structures should be provided with a drainage system, as illustrated on Figure F- 1, Retaining Wall Backfill and Subdrain Detail, to prevent buildup of hydrostatic pressure behind the wall. In addition to the recommended earth pressures, walls below grade adjacent to existing structures or streets and areas of traffic should be designed to accommodate surcharge loads. For traffic surcharge, a uniform lateral pressure of 100 pounds per square foot acting as a result of an assumed 300 pounds per square foot surcharge behind the wall due to normal traffic; the traffic surcharge load may be neglected provided a minimum of 10 foot clearance between the wall and the traffic is maintained. We will provide surcharge loading from -24- Leighton