GATE Civil Engineering (CE) 2016 Shift 1 Solved Paper

An undisturbed soil sample was taken from the middle of a clay layer (i.e., 1.5 m below GL), as shown in figure. The water table was at the top of clay layer. Laboratory test results are as follows:
The natural water content of clay: 25%
Preconsolidation pressure of clay: 60 kPa
Compression index of clay: 0.50
Recompression index of clay: 0.05
Specific gravity of clay: 2.70
Bulk unit weight of sand: 17 kN/m³
A compacted fill of 2.5 m height with a unit weight of 20 kN/m³ is placed at the ground level.

Assuming unit weight of water as10 kN/m³ , the ultimate consolidation settlement (expressed in mm) of the clay layer is ____________