A $1\mathrm{.}5m$ deep square footing $(B=L=1\mathrm{.}0(m),D_f=1\mathrm{.}5(m))$ carries a downward load of $250kN.$ It is underlain by over$-$

consolidated clay $($OC case $1)$ with the following properties: $C_c=0\mathrm{.}20,C_r=0\mathrm{.}05,e_0=0\mathrm{.}7$ and ${}_n=17\mathrm{.}0k\frac{N}{m^3}$

$($above the groundwater table$)$ and ${}_{\text{s}\text{a}\text{t}}=18\mathrm{.}0k\frac{N}{m^3}($below the groundwater table$).$ The groundwater table is

at a depth of $1\mathrm{.}5m$ below the ground surface. The secondary compression settlement is negligible. Determine

the coefficient of subgrade reaction.