1212 GRAND AVE 2016-01-01 MF Import

March 31, 2008 Mr. Paul Tessier L&A Job No. RA027 Pagc 11 Lateral loads on the existing house, ihe additions and the new garage can E: resisted by the friction force between the foundations and the subgrade soils or the passive earth pressure acting on the below-grade portion of the foundations. For the latter, the foundations must be poured "neaf' against undisturbed soils or backfilled with a clean, fine-draining, compacted structural fill. We recommend that an equivalent fluid density (EFD) of 350 pcf(pounds per cubic foot) for the passive carth pressurc be used for latcral resistance. Thc above passive pressure assumes that the backfill is Icvel or inclines upward behind the foundations for a horizontal distance at least twice the depth of thc foundations below 6nal grade. A coeflicient of friction of 0.60 between the foundations and the subgrade soils may be used. 7'hese arc unfactored valucs, and a proper factor of safcty should be used in calculating the resisting forces against lateral loads on the buildings. BASEMENT WALLS The basement walls or cxtended footing walls of the proposed additions and ncw garage would be restrained at the top tiom lateral movement and should be dcsigncd for a lateral soil prcssure under the at-rest condition. We recommend that an at-rest soil pressure of 45 pcf EFD (equivalent fluid density) bc used for thc design of basement walls or extended footing walls. To counter the above active soil pressurc, a passive lateral soil pressure of 350 pcf EFD may be used. 1'o rcsist against sliJing, the friction force txtween the footings and the subecade soils may be calculated based on a ccetTicient of friction of 0.60. 'I'he above soil parameters are ultimate values based on a fully draincd condition of thc walls, and pro�;r factors of safety factors should be applied in the design of the basement walls or extenJed footing walls against sliding and ovcrtuming failures. A vertical drainage blanket, at Icast 12-inch-thick horizontally, consisting of clean, free-drnining, pea gravcl or washed gravcl, should be placed against the back of bascment or extendcd footing LIU & ASSOCIATES, INC. ;.��.. 1