2824 GRAND AVE NAUTICA CONDOMINIUMS 2018-01-02 MF Import

GEOTECHNICAL ENGINEERING STUDY Cascasia Pacific Properties, Ltd. July 15, 1999 E-8602 Page 13 Liquefaction is a phenomenon in which soils lose all shear strength for short periods of time during an earthquake. The effects of liquefaction may be large total and/or differential settlement for structures with foundations founded in the liquefying soils. Groundshaking of sufficient duration results in the loss of grain -to -grain contact and rapid increase in pore water pressure, causing the soil to behave as a fluid for short periods of time. To have potential for liquefaction, a soil must be cohesionless with a grain size distribution of a specified range (generally sands and silt); it must be loose to medium -dense; it must be below the groundwater table; and it must be subject to sufficient magnitude and duration of groundshaking. Eased on the soil and groundwater conditions observed at the site, it is our opinion that the site has a low susceptibility to liquefaction. The absence of an established groundwater table and the medium dense to dense condition of the native soils is the primary basis for this conclusion. Permanent Retaining and Foundation Walls Retaining and foundation walls should be designed to resist lateral earth pressures from the retained soils, and anv surcharge loading. For walls designed to yield a minimum of 0.002 times the height of the wall, lateral earth pressures can be calculated using an equivalent fluid with a unit weight of thirty-five (35) pounds per cubic foot (pcf). For non -yielding walls, the equivalent fluid pressure should be increased to fifty (50) pcf. The above lateral earth pressure values assume horizontal backfill conditions. The above lateral earth pressure values assume no surcharges due to traffic, adjacent foundations, construction loads, or other loading. If surcharges are to apply, they should be added to the above design lateral pressures. A two foot soil surcharge should be used to account for traffic surcharges, where applicable The walls should be provided with a perforated drain pipe and backfilled with a free -draining material. The free -draining material should extend at least eighteen (18) inches behind the wall. The remainder of the backfill should consist of structural fill. The use of a sheet drain such as Mira -Drain 6000 or equivalent can be considered in lieu of free draining backfill. In areas where temporary shoring is used, the use of a sheet drain placed along the inside face of the lagging will be necessary. In these areas, weep holes will be required to allow water to pass through the wall and into a drain system. Eenh Caneuhants, Inc.