Example $7\mathrm{.}5$: The settlement analysis $($based on the assumption of the clay layer draining

from top and bottom surfaces$)$ for a proposed structure shows $2\mathrm{.}5$ cm of settlement in four

years and an ultimate settlement of $10$ cm $.$ However, detailed sub$-$surface investigation re$-$

veals that there will be no drainage at the bottom. For this situation, determine the ultimate

settlement and the time required for $2\mathrm{.}5$ cm settlement.