A caisson is being used to construct a bridge pier $5$m of water. It is sunk through very soft clay $3$m into a stiff clay with properties given in Table B$18-1.$The caisson is $15$m in diameter $($external$)$ and formed of $0\mathrm{.}75$m thick reinforced concrete units. The base of the caisson after it is installed is a $3$m thick reinforced concrete raft integral with the walls of the caisson. The raft is designed to carry a permanent load of $5000$T$.$ Assume the top of the caisson is always at least $1$m above water level. Estimate the settlement of the caisson.