7000 HARDESON RD 2018-01-02 MF Import

Quadrant 6-917-10260 12 April 1996 Page 7 0.1 percent of the height of the wall, the soil pressure will be less than if structurally restrained from lateral movement at the top. Retaining walls an be designed using an equivalent fluid pressure of 35 pcf (pounds per cubic foot) and 50 pcf be used for yielding and non -yielding backfllled walls, respectively. Allowable passive pressure values should be designed for on I equivalent fluid weight of 350 pcf neglecting the upper 1 foot of soil and assuming a factor of safety of at least 1.5. These equivalent fluid pressures assume that the backfill is compacted to 90 percent of the modified Proctor maximum dry density (ASTM:D 1557). We recommend that AEE be allowed to review these design values, and modify them if necessary, if they are to be applied to walls greater than 12-feet in height. We recommend an allowable base friction value of 0.4, utilizing a factor of safety of 1.5. The above equivalent fluid pressures are based on the assumption of a uniform horizontal backfill and no build-up of hydrostatic pressure behind the wall. Surcharge pressures due to sloping ground, adjacent footings, vehicles, construction equipment, etc., must be added to these values. Sloping surcharges within a distance from the top of the wall equal to the height of the wall should be factored into the wall design. The equivalent lateral surcharge of the slope within the distance previously described should be equal to % or % the height of the slope times a unit weight of 130 pcf for active and attest conditions, respectively. A minimum width of 2 feet of clean, granular free -draining material should extend from the footing drains at the base of the wall to within one foot of the ground surface, to prevent the buildup of hydrostatic forces. Wall backfill should consist of aggregate with less than 3 percent passing the U.S. No. 200 Sieve, based on that fraction passing the U.S. No. 4 Sieve, with at least 30 percent retained on the No. 4 Sieve. The upper foot of wall backfill should be silty soils to cap the free -draining fill and reduce infiltration adjacent to the wall. Filter fabric should be placed over the top of the drainage materials to segregate it from the overlying silty soils. It should be realized the primary purpose of the free -draining material is reduction of hydrostatic pressure. Some potential for moisture to contact the back face of the wall may exist event with this treatment, which may require more extensive waterproofing to be specified for wells which require interior moisture -sensitive finishes. Service pit walls do not require clean, granular free -draining material for backfill. We do not anticipate excessive hydrostatic pressures as concrete pavement and building slabs will greatly reduce the infiltration of water. Fill material should conform to specifications from Section 4.2 'Structural Fill". On -site soil would he permissible provided adequate compaction can be A achieved. To prevent the buildup of lateral earth pressures in excess of the above design pressure, overcompaction of fill immediately behind the walls should be avoided. Only light self-propelled or hand compaction equipment should be allowed within close proximity to the wall. Bacltflll placed behind walls should be placed in accordance with our recommendations for structural fill, except the maximum compacted fill density should not exceed 90 percent of the modified Proctor maximum dry density. j �2L