Question

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

• A. 20.56

Answer 1

The correct option is A 20.56

Primary consolidation settlement is given by,
$\Delta H=\frac{C_c{H}_c}{1+e_0}lo{g}_{10}\left[\frac{\overline{{\sigma }_0}+\Delta \overline{\sigma }}{\overline{{\sigma }_0}}\right]$
Void ratio $e_0=\frac{wG}{S}=\frac{0.40\times 2.7}{1}=1.08[\because$ Soil is saturated]
$\Delta H=\frac{0.45\times 1.2}{1+1.08}{\log }_{10}\left[\frac{125+25}{125}\right]$
$=0.02056m=20.56\text{mm}$