See.t $22/66$

Q$1.$ A square foundation $(22)$ m carries a load P and is to be found at $1\mathrm{.}8$ m below the ground surface. The underlying soil is sand with undrained shear strength, $c^{\text{'}}=20$kPa,${}^{\text{'}}=28,=17k\frac{N}{m^3}.$ The groundwater table is at the bottom of the foundation level.

Determine

a$.$ the allowable bearing capacity

Use a safety factor of $3.$

Include $W_f.$ Assume all is concrete, use ${}_{\text{c}\text{o}\text{n}\text{c}\text{r}\text{e}\text{t}\text{e}}=23\mathrm{.}6k\frac{N}{m^3},{}_w=9\mathrm{.}81k\frac{N}{m^3}$

b$.$ the Allowable bearing capacity if the water table dropt below the bottom of the foundation level.