Q$4)($a: $8\%,$ b: $8\%,$ c: $4\%)$

Foundation of an oil storage tank is located $2m$ below the surface of a clay deposit which is $17$

$m$ thick. A firm stratum underlies the clay. Diameter of the tank is $10m$ and the gross foundation

pressure is $165$kPa. The average value of coefficient of volume compressibility of the clay is

$0\mathrm{.}14\frac{m^2}{M}N.$ The saturated unit weight is $20k\frac{N}{m^3}$ and the undrained elastic modulus is

estimated to be $25$MPa.

a$)$ Calculate the average immediate $($elastic$)$ settlement of the foundation, using net

foundation pressure.

b$)$ Calculate the consolidation settlement of the foundation using approximate method

of stress distribution. In your calculation, subdivide the clay into two sublayers such that

the upper and lower are respectively $5m$ and $10m$ thick. Apply a Skempton$-$Bjerrum

correction factor of $0\mathrm{.}85$ to the oedometric settlement.

c$)$ If the angular rotation limit for the tank structure is provided as $\frac{1}{125},$ calculate the

allowable differential settlement between the center and edge of the tank foundation.