Problem $3$: A square foundation is $3mx3m$ in plan. The water table is at $6$ meters depth. The soil supporting the foundation has a friction angle ${}^{\text{'}}=10$ and $c^{\text{'}}=30k\frac{N}{m^2}.$ The dry unit weight of soil ${}_{\text{d}\text{r}\text{y}}=16k\frac{N}{m^2}$ and saturated unit weight of soil ${}_{\text{s}\text{a}\text{t}}=20k\frac{N}{m^2}.$ Determine the allowable gross load on the foundation with a factor of safety $($FS$)$ of $3.$ Assume the depth of the foundation $(D_f)$ is $1\mathrm{.}5m$ and that general shear failure occurs in the soil. Hint: