Q. A 4 m wide strip footing is founded at a depth of 1.5 m below the ground surface in a c−ϕ soil as shown in the figure. The water table is at a depth of 5.5 m below ground surface. the soil properties are c' = 25 kN/m2, ϕ′ = 28.63o, γsat = 19 kN/m3, γbulk = 17 kN/m3 and γw = 9.81 kN/m3. the values of bearing capacity factors for different ϕ′ are given below.
ϕ′NcNqNγ15∘12.94.42.520∘17.77.45.025∘25.112.79.730∘37.222.519.7
Using Terzaghi's bearing capacity equation and a factor of safety Fs=2.5, the net safe bearing capacity (expressed in kN/m2) for local shear failure of the soil is