Soil Mechanics

Footings for a structure are to be built beneath a basement slab on a clay at a depth of 20 ft. below present ground level. Representative consolidation tests on the soil produce a 0.043 slope of recompression curve. The groundwater table is 15 ft. below the ground surface. The soil has a unt weight of 120 pcf. The soil-void ratio is about 0.87. If the average bearing pressure on the footings is 2,600 psf., estimate the settlement of 10 ft. and 5 ft. square footings. Also , what is the factor of safety for the footings against bearing failure if the clay soil has an unconfined compressive strenght of 3,600 psf? The back of the book says that for a 5 ft. footing, the estimated settlement= 1.72 in. And for a 10ft. footing, the estimated settlement= 2.42 in. Also it says the Factor of Safety at least for the 5 t. footing is FS=5.554