Question $4$

A rectangular foundation $2\mathrm{.}5m$ wide by $3\mathrm{.}5m$ long is to carry a

total load of $1\mathrm{.}3MN.$ The water table is at $1\mathrm{.}2m$ below ground

level and the site has a thick deposit of firm saturated clay with

the following properties:

$C_u=65$kPa,${}_u=0,{}_{\text{s}\text{a}\text{t}}=21k\frac{N}{m^3}$

a$)$ Calculate the factor of safety against bearing capacity failure if

the foundation is placed at ground surface.

b$)$ If the foundation is to be located at $1\mathrm{.}7m$ below ground level, re$-$

evaluate the factor of safety. Comment briefly on the change in

safety factor.

c$)$ State which type of triaxial test you would conduct to determine

the strength parameters required for this problem. Give a brief

explanation.

d$)$ Briefly describe the typical triaxial compression test results

expected of undrained tests on normally and overconsolidated

clays. Use sketches of the sample response of deviator stress

and pore water pressure with axial deformation.