5. (a) A sample of clay in a triaxial apparatus is subjected to a

standard undrained compression test. At the start of the test

the pore pressure is 200 kN/m² and the cell pressure is 300

kN/m². The sample fails when the deviator stress reaches a

value of 62 kN/m² and the pore pressure has increased to 250

kN/m². Draw total stress and effective stress Mohr's circles for

the sample at failure. What is the drained angle of friction of

the clay?

(10 marks)

BEng Civil Engineering -Soil Mechanics-Referred /Deferred Coursework

5

(b) Table 4 gives an extract of results from a shear box test on a

dry sand soil, subjected to different normal stress levels. The

results shown in the table have already been processed in

terms of shear stresses for different normal stress levels.

Determine the ultimate angles of friction for the soil.

(10 marks)

Total 20 marks