Question 1 A 5-m depth of sand overlies a 6-m layer of clay, the water table being at the surface. The saturated unit weight of the sand is 19 kN/m3 and that of the clay is 20 kN/m³. Use the unit weight of water (Yw) is 9.81 kN/m³. (a) Determine the total and effective vertical stresses at the centre of the clay layer. (b) The coefficient of lateral earth pressure at rest, Ko, of the clay is identified as 0.8. Calculate the total and effective horizontal stresses at the centre of the clay layer. Depth (m) G.W.L 0.0 Sand 5.0 8.0 -- Clay 11.0 Bedrock

A level ground surface exists in an area where soil in the underlying stratum has a wet unit weight of 19 kN/m3. The vertical pressure at any depth represents the major principal stress. The vertical pressure (stress) is the product of the soil unit weight and depth. The lateral pressure at a corresponding depth is 0.45 times the vertical pressure and represents the minor principal stress. (a) Determine the principal stresses acting at a depth 4 m below the surface, and draw the Mohr’s circle for the condition. (b) What is the maximum shear stress acting at this depth?