Example Problem 6.17 For cohesionless surface layer (effective tress analysis)—Use the
same data, but assume the 3 m thick unliquefiable surface layer is sand with an effective friction
angle f′ equal to 32°, a coefficient of earth pressure at rest (k ) equal to 0.5, and a total unit
weight = 18.3 kN/m 3 o . Also assume that the groundwater table is at a depth of 3 m below the
existing ground surface. Calculate the factor of safety of the footings using Eqs 6.30 and 6.31.