(b) An embankment slope consisting of a granular fill is underlain by a deep deposit of clay of specific gravity of 2.65. The granular fill has a bulk unit weight of 19.3 kN/m3, effective cohesion, c =7.2kPa and internal friction angle, =30. If the clay soil has varying moisture content and undrained shear strength at different times of the year as presented in Table 1, investigate the stability of the embankment slope using the slip circle shown in Figure 1. How does the varying soil properties influence the stability of the slope? Draw the slope to scale on a graph paper or using CAD and split the sliding section up into a suitable number of slices. Table 1. Properties of clay

Property
Moisture content (%)	27	30	35	40
Void ratio	0.71	0.55	0.5	0.48
Undrained shear strength (kPa)	32.5	28	20	18

(c) Assume that the ground water level is located at the top of the clay layer in Figure 1, and the clay layer has c = 75kPa, =7^o, = 19kN/m3, calculate the factor of safety, and compare with the values calculated in (b) above.

4.57 m Granular fill 9.15 m 7.64 m Clay 9.15 m Figure 1. 4.57 m Granular fill 9.15 m 7.64 m Clay 9.15 m Figure 1