QUESTION $4($Foundations$)$

$($a$)$ The diagram below shows a square $2m2m$ concrete footing located at a depth of $1$

$m$ below ground surface. The height of the footing is $0\mathrm{.}3m.$ It supports a central

column load of $900kN$ which includes the weight of the column. The soil properties

are shown on the diagram. The water table is more than $2m$ below the surface.

$($i$)$ Calculate the uniformly distributed stress imposed on the soil immediately

below the footing by the combined effect of the $900kN$ load and the weight

of the footing. Take the unit weight of concrete $=24k\frac{N}{m^3}.$

$($ii$)$ Calculate the ultimate bearing capacity of the soil below the footing, and

hence the safety factor against shear failure under the applied stress

calculated in $($i$)$ above.