Question

Calculate the vertical stress at a depth of 3m below the ground surface due to weight of the soil whose unit weight is 18.5KN/m^3. Assume the water table is at a depth of (a) 5m (b) 2m

Answer 1

Vertical stress below 3m ground level..

when Ground water table(G.W.T) is at 5 m from the ground surface::
there is no effect of pore water pressure at 3m..
so,,effective vertical stress at 3m = (unit wt X thickness of soil) =18.5 * 3 = 55.5 KN/m^2...

when Ground water table(G.W.T) is at 2 m from the ground surface::
there is effect of porewater pressure that results in decrease in effective stress...
so,,effective vertical stress at 3m= (unit wt X thickness of soil) - (9.81 * 1) = 45.69 KN/m^2