The properties of seven different clayey soils are shown below (Skempton and Northey, 1952). Investigate the relationship between the strength and plasticity characteristics by performing the following tasks:
a. Estimate the plasticity index for each soil using Skempton's definition of activity [Eq. (4.26)].
b. Estimate the probable mineral composition of the clay soils based on PI and A (use Table 4.2).
c. Sensitivity (St) refers to the loss of strength when the soil is remolded or disturbed. It is defined as the ratio of the undisturbed strength (tf -undisturbed) to the remolded strength (tf -remolded) at the same moisture content [Eq. (12.38)]. From the given data, estimate tf -remolded for the clay soils.
d. Plot the variations of undisturbed and remolded shear strengths with the activity, A, and explain the observed behavior.

% Clay Undlsturbed shear Soll fraction ( < 2 pm) Actlvlty, A strength (KN/m Senslvlty, S, Detroit I Horten Gosport Mexico City Shellhaven St. Thuribe 79 36 40 0.52 0.36 0.42 0.89 4.5 1.33 0.33 18 17 41 29 46 2.5 17 2.2 5.3 7.6 90 41 38 150