Problem 8 a) Using the Boussinesq approach, determine the vertical stress increase beneath a point load of 200 kN at: i) depths of 1 and 3 meters directly below the point of loading ii) at the same depths but with horizontal offsets of 1.5 m in the x and y directions. b) A 3 by 6 m concrete slab is cast directly on the surface of the ground. The slab uniformly carries a total load of 1800 kN. The soil beneath the slab has a dry unit weight of 16.8 kN/m, a specific gravity of solids 2.68 and a moisture content of 17.4% from the surface down to the water table which is at a depth of 1.50 m; the soil is saturated below the water table. (Hint: Use the phase diagram concepts to calculate the total unit weight above the water table and the saturated unit weight below the water table) i) Calculate the total and effective stresses at a depth of 3 m prior to the construction of the slab. ii) Calculate the increase in vertical total stress due to the slab load and the final total stress at a depth of 3 m directly below the center of the slab. iii) Calculate the increase in vertical total stress due to the slab load at a depth of 3 m under one corner of the slab.