Example $14\mathrm{.}21$: A foundation $2m3m$ is resting at a depth of $1$ m below the ground surface.

The soil has a unit cohesion of $10k\frac{N}{m^2},$ angle of shearing resistance of $30$ and unit weight of

$20k\frac{N}{m^3}.$ Find the ultimate bearing capacity using Balla's method.