A square concrete plle, $400-mm400-mm,$ is

required to support an allowable load of

$150kN$ with a factor of safety of $3.$ The soil

layers consist of $3m$ of soft clay, underlain

by a deep layer of stiff clay.

Assume the unit weight of concrete to be

$24k\frac{N}{m^3}.$ Calculate:

$1\mathrm{.}0$ The ultimate load, in $kN.$

$2\mathrm{.}0$ The total required length, $L$

of the pile in meters.