Question $2$

The orebody described in Problem $1$ above is underlain by a clay shale, for which

$c=1\mathrm{.}2$MPa,$=28,$ and $=22k\frac{N}{m^3}.$ If the mining layout is based on $6\mathrm{.}0$ m

room spans and pillars $10\mathrm{.}0$ m square in plan, determine the factor of safety against

bearing capacity failure of the floor rock.

Ans: FOS$=5\mathrm{.}5$

The correct answer is provided $-$ please ensure its maths. ty$.$