$12\mathrm{.}36$ Figure P$12\mathrm{.}36$ shows a $35$ pile group consisting of

$15$ concrete piles of $400$ mm diameter and $12$ m in length.

What would be the maximum load that can be allowed on

the mat with a factor of safety of $3?$ The piles have a center$-$

to$-$center spacing of $1200$ mm $.$

FIGURE P$12\mathrm{.}36$