The following data was obtained from a single loading increment of $50$kPa

during an oedometer test on soil sample. The sample thickness was $20$mm

ONLY ANSWER THIS Q $($value of cv $=0\mathrm{.}85$ m$2/$yr$)$

using the value for cv calculated in Part $1$ determine the

time for $90\%$ consolidation of the $3m$ thick clay layer shown in the figure

below, where a relatively impermeable embankment is to be constructed

on top of the clay layer.