Practice Question: Evaluating Factor of Safety Against Heave in Clayey Soil

NCEES Civil PE Specification Design for Support of Construction Loads: Support of excavation


An excavation support system is provided to support excavation with the following dimensions: 
Length = 500 ft, Width = 50 ft, Depth = 25 ft. 
The soil consists of clay with a shear strength (Su) of 1,200 lb/ft2 and a unit weight of 125 lb/ft3. Notably, stiff material is encountered at a depth of 20 ft below the base of the excavation. The factor of safety against Heave is most nearly:

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