A square spread footing is located on a stiff clay layer underlayed by a soft clay deposit.

Compute the allowable bearing capacity of the footing and the minimum thickness of the stiff clay layer to assure a FS = 3 on the soft clay deposit. Since the footing is resting on a stiff stratum of soil, the bearing capacity will be calculated assuming a general failure mode, by means of Terzaghi's bearing capacity theory. That solves part (a). For part (b), it is necesary to compute the stress distribution beneath the footing to check the stress increment in the soft clay layer. The stress distribution will be computed using Boussinesq's theory.