2211 GIBSON PL Geotech Report 2023-04-06

August 18, 2014 Gibson Bluff L&A Job No. 14-056 Page 14 supported on medium-dense to dense Esperance sand soil under the above allowable soil bearing pressure, we estimate that the maximum total post-construction settlement of the buildings should be 3/4 inch or less and the differential settlement across building width should be 1/2 inch or less. Lateral loads can be 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 "neat" against undisturbed soils or backfilled with a clean, free-draining, compacted structural fill. We recommend that an equivalent fluid density (EFD) of 300 pcf(pounds per cubic foot) for the passive earth pressure may be used for lateral resistance. The above passive pressure assumes that the backfill is level or inclines upward behind the foundations for a horizontal distance at least 1.5 times the depth of the foundations below final grade. A coefficient of friction of 0.55 between the foundations and the subgrade may be used. These soil parameters are unfactored ultimate values, and a proper factor of safety should be used in calculating the resistance against lateral loads on the buildings. Building Foundation Walls Building foundations walls, if also serving as retaining walls, should be designed for lateral soil pressure. Foundation walls restrained at the top from lateral movement are considered unyielding and should be designed for a lateral soil pressure under the at-rest condition. We recommend that an at-rest soil pressure of 50 pcf EFD (equivalent fluid density) be used for the design of foundation walls with a level or descending backslope. LIU & ASSOCIATES, INC.