List of top Geotechnical Engineering Questions on One-dimensional consolidation

The soil profile at a construction site is shown in the figure (not to scale). Ground water table (GWT) is at 5 m below the ground level at present. An old well data shows that the ground water table was as low as 10 m below the ground level in the past. Take unit weight of water, \( \gamma_w = 9.81 \, \text{kN/m}^3 \).

The overconsolidation ratio (OCR) (round off to two decimal places) at the mid-point of the clay layer is \(\underline{\hspace{1cm}}\).

A clay layer of thickness \( H \) has a preconsolidation pressure \( p_c \) and an initial void ratio \( e_0 \). The initial effective overburden stress at the mid-height of the layer is \( p_0 \). At the same location, the increment in effective stress due to applied external load is \( \Delta p \). The compression and swelling indices of the clay are \( C_c \) and \( C_s \), respectively. If \( p_0 < p_c < (p_0 + \Delta p) \), then the correct expression to estimate the consolidation settlement \( s_c \) of the clay layer is

The soil profile at a road construction site is as shown in figure (not to scale). A large embankment is to be constructed at the site. The ground water table (GWT) is located at the surface of the clay layer, and the capillary rise in the sandy soil is negligible. The effective stress at the middle of the clay layer after the application of the embankment loading is 180 kN/m\(^2\). Take unit weight of water, \( \gamma_w = 9.81 \, \text{kN/m}^3 \).

The void ratio of a clay soil sample M decreased from 0.575 to 0.510 when the applied pressure is increased from 120 kPa to 180 kPa. For the same increment in pressure, the void ratio of another clay soil sample N decreases from 0.600 to 0.550. If the ratio of hydraulic conductivity of sample M to sample N is 0.125, then the ratio of coefficient of consolidation of sample M to sample N (round off to three decimal places) is \(\underline{\hspace{1cm}}\).