Example $9\mathrm{.}7$: At cut $9$ m deep is to be made in a clay with a unit weight of $18k\frac{N}{m^3}$ and a

cohesion of $27k\frac{N}{m^2}.$ A hard stratum exists at a depth of $18$ m below the ground surface.

Determine from Taylor's charts if a $30$ slope is safe. If a factor of safety of $1\mathrm{.}50$ is desired, what

is a safe angle of slope?