Example $16\mathrm{.}9$: A reinforced cement concrete pile weighing $30$ kN $($including helmet and dolly$)$

is driven by a drop hammer weighing $30$ kN with an effective fall of $0\mathrm{.}9$ m $.$ The average pen$-$

etration per blow is $15$ mm $.$ The total temporary elastic compression of the pile, pile cap and

soil may be taken as $18$ mm $.$ Coefficient of restitution $0\mathrm{.}36.$ What is the allowable load on the

pile with a factor of safety of $2?$ Use Hiley's formula.