A layer of normally consolidated, saturated silty clay of 1.2 m thickness is subjected to one dimensional consolidation under a pressure increment of 25 kPa. The properties of the soil are: Specific gravity = 2.7. natural moisture content = 40% and compression index 0.45. The initial average effective stress within the layer is 125 kPa. Assuming Terzaghi s theory to be applicable, the primary consolidation settlement is mm