Example $8\mathrm{.}3$: Calculate the potential shear strength on a horizontal plane at a depth of $3$ m

below the surface in a formation of cohesionless soil when the water table is at a depth of $3\mathrm{.}5$

m $.$ The degree of saturation may be taken as $0\mathrm{.}5$ on the average. Void ratio $=0\mathrm{.}50$; grain

specific gravity $=2\mathrm{.}70$; angle of internal friction $=30.$ What will be the modified value of shear

strength if the water table reaches the ground surface?