In this question , i suspect the total vertical stress at the center of the clay is incorrect .
The Attempt at a Solution
In the figure , we can see that the water table is art 2m below the sand . So , the 2m sand thick should be dry , am i right ? Only the 1m thick sand is moist / saturated with water .
so , when we are calculating the vertical stress , we have to divide the soil into 2 parts , which are (dry unit weight of soil x 2m ) + ( saturated unit weight of soil x 1m) + ( saturated unit weight of clay x 2m)