Question

Plate load test is adopted globally to determine in-situ bearing capacity of the subsoil and considered as one of the most important field test for any big construction project. A plate load test was conducted on a 300 mm side square plate at a depth of 1.10 m below the ground level in pure clayey soil for an important construction site. Failure of the soil occurred at a load of 45 kN. A. Calculate the safe bearing capacity of a 1.5 m wide square footing founded at a depth of 1.5 m in the same sub-soil. Assume the total unit weight and factor of safety of 18.2 kN/m3 and 2.0 respectively

Answer 1

for a clayey soil

ultimate bearing capacity = ultimate load on the plate

Qu = load on plate / area

Qu = 45 kN / (.3 * .3)

Qu = 500kN/ m2

safe bearing capacity = Qu/ factor of safety

sbc = 500/2 = 250 kN / m2

total load that can be bear by the footing = (safe bearing capacity * area of footing) - weight of soil

(250 * 1.5*1.5) - ( area * depth * density of soil)

(562.5) - ( 1.5* 1.5* 1.5 * 18.2)

501.075 kN

hence the bearing capacity of soil is 250 kN/m2 and the load bearable by footing is 501.075 kN.