QUESTION $4$

$($a$)$ The data in Table Q$4$ are from an undrained triaxial test on a sample of clay. The

initial dimensions of the sample were $76mm$ in length and $38mm$ in diameter. During

the test the cell pressure was constant at $500$kPa. Plot the effective stress path for this

test on q$\text{'}$:p$\text{'}$ axes.

$[15$ marks$]$

TURN OVER

CEGE$0100$

Page $5$ of $6$

Table Q$4$

$($b$)$ Is this clay normally or overconsolidated?

$[2$ marks$]$

$($c$)$ Assuming that the last data point is the state at which the soil fails, calculate the

critical state line gradient $M$ and the undrained shear strength $S_u.$

$[4$ marks$]$

$($d$)$ Sketch the Mohr's circle of effective stresses at failure, indicating the values of the

principal stresses and hence calculate the critical state friction angle $\text{'}$cs$.$