A 2-m clay layer in the field has a current effective stress, '0 = 70 kN/m2. There is a net stress increase, = 180

A 2-m clay layer in the field has a current effective stress, σ'0 = 70 kN/m2. There is a net stress increase, Δσ = 180 kN/m2, due to a foundation load. Calculate the expected primary consolidation settlement. The results of a consolidation test on the clay are given below.
eσ' (kN/m2)
0.98..................12
0.94..................50
0.82................200
0.73................400