3400 RIVERFRONT BLVD Geotech Report 2022-10-25

• • • • 6.12.2 Resistance to Sliding • Lateral loads on footings can be resisted by passive earth pressure on the sides of the structures • and by friction on the base of the footings. An allowable passive resistance may be calculated as a triangular pressure distribution, using an equivalent fluid density of 300 pcf. The upper • 12 inches of adjacent unpaved areas should not be considered when calculating passive 40 resistance. A coefficient of friction equal to 0.30 may be used when calculating resistance to • sliding for foundations in direct contact with sand and silt. Foundations in contact with crushed • rock should be designed using a coefficient of friction of 0.40. • 6.13 UTILITIES • We understand that new utilities will be installed as part of this project. These utilities will cross • the site, including areas with different subsurface conditions. We recommend that these utilities be designed to account for 2 inches of long-term settlement and 1 inch of differential settlement • over a distance of 100 feet. The "Seismic Hazards" section of this report describes additional • seismic settlement that could occur during a design-level earthquake. • 6.14 RETAINING STRUCTURES • 6.14.1 Assumptions • Our retaining wall design recommendations are based on the following assumptions: (1)the 410 walls consist of conventional, cantilevered retaining walls, (2)the walls are less than 12 feet in height, (3) the backfill is drained and consists of imported granular material, and (4)the backfill has a slope flatter than 4H:1 V. Re-evaluation of our recommendations will be required if the • retaining wall design criteria for the project varies from these assumptions. • • 6.14.2 Wall Design Parameters • For unrestrained retaining walls, an active pressure of 35 pcf equivalent fluid pressure should be • used for design. Where retaining walls (such as basement stem walls) are restrained from rotation prior to being backfilled, a pressure of 55 pcf equivalent fluid pressure should be used • for design. A superimposed seismic lateral force should be calculated based on a dynamic force . of 7H2 pounds per linear foot of wall (where H is the height of the wall in feet). The load should . be applied as a distributed load with the centroid located at a distance of 0.6H above the base of the wall. • • If surcharges (e.g., retained slopes, building foundations, vehicles, terraced walls, etc.) are • located within a horizontal distance from the back of a wall equal to the height of the wall, then . additional pressures will need to be accounted for in the wall design. Our office should be contacted for appropriate wall surcharges based on the actual magnitude and configuration of • the applied loads. • • The base of the wall footing excavations should extend a minimum of 18 inches below the lowest adjacent grade. The wall footings should be designed in accordance with the guidelines • provided in the appropriate portion of the "Foundations" section of this report. At locations • where there is a slope in front of the retaining wall, we recommend that a minimum 5-foot-wide, • horizontal bench be placed between the wall and the top of the slope. • • G EODESIGNZ 20 Polygon-128-01:091615 •