A series of columns carrying unfactored vertical loads of 20 to 90 k and service loads from 20 to 75 k are to be supported on 3 ft deep square footings. The soil below is a clay with the follow- ing...

A series of columns carrying unfactored vertical loads of 20 to 90 k and service loads from 20

to 75 k are to be supported on 3 ft deep square footings. The soil below is a clay with the follow-
ing engineering properties: g = 105 lb/ft

3
above the groundwater table and 110 lb/ft
3
below,

su = 3,000 lb/ft
2
, Cr/(1 + e0) = 0.03 in the upper 10 ft and 0.05 below. Both soil strata are
heavily overconsolidated. The groundwater table is 5 ft below the ground surface. The factor
of safety against a bearing capacity failure must be at least 3. Determine the allowable bearing
pressure, qA, using ASD.