$2\mathrm{.}17$ A clay specimen $25mm$ thick $($drained at top only$)$ was tested in the laboratory. For a given load increment, the time for $60\%$ consolidation was $6$min. How long will it take for $50\%$ consolidation for a similar clay layer in the field that is $2\mathrm{.}45m$ thick and drained on both sides?

Answer:

$6\mathrm{.}87$ days