Given: $D_f=1\mathrm{.}5m,=15\mathrm{.}9k\frac{N}{m^3},{}^{\text{'}}=34,$ and $c^{\text{'}}=0.$ Assuming general shear failure, use Terzaghi's equation to

determine the size of a square foundation $(B)$ required to carry an allowable load $Q_a$ of $1805$ kN with a factor of safety

$($FS$)$ of $3,$ based on the requirement of either $(1)$ or $(2)$ below.

$(1)$ FS is applied to the gross bearing capacity.

$(2)$ FS is applied to the net bearing capacity