PC-2025-16 - Laserfiche WebLink

ENGEO INCORPORATED 5150.100.101 May 2, 2008 Page 23 9. RETAINING WALLS Due to the anticipated seepage at the cuts for the walls, temporary vertical cuts may not be stable. This condition may necessitate temporary shoring or top-down wall construction such as soil nail or cement-soil mixed walls. 9.1 LATERAL SOIL PRESSURES Design proposed retaining walls to resist lateral earth pressures from adjoining natural materials and/or backfill and from any surcharge loads. Provided that adequate drainage is included as recommended below, design walls restrained from movement at the top to resist an equivalent fluid pressure of 65 pounds per cubic foot (pcf). In addition, design restrained walls to resist an additional uniform pressure equivalent to one-half of any surcharge loads applied at the surface. Design unrestrained retaining walls with adequate drainage to resist an equivalent fluid pressure of 50 pcf plus one-third of any surcharge loads. The above lateral earth pressures assume level backfill conditions and sufficient drainage behind the walls to prevent any build-up of hydrostatic pressures from surface water infiltration and/or a rise in the groundwater level. If adequate drainage is not provided, we recommend that an additional equivalent fluid pressure of 40 pcf be added to the values recommended above for both restrained and unrestrained walls. Damp-proofing the walls should be included in areas where wall moisture would be problematic. Construct a drainage system, as recommended below, to reduce hydrostatic forces behind the retaining wall.