Question $6$:

$($Value: $30$ marks$)$

Table $1$ summarizes the results of three series of consolidated$-$undrained $(\frac{?}{\text{b}\text{a}\text{r}}(CU))$ triaxial

tests with pore water pressure measurements on fully saturated clay specimens at failure

conditions.

Table $1.$ Consolidated undrained $(\frac{?}{\text{b}\text{a}\text{r}}(CU))$ triaxial test results at failure

$($i$)$ Determine the effective shear strength parameters for the tested soil by plotting the

modified failure envelope.

$(10$ marks$)$

NATIONAI, F$.$XAMINATIONS $-$ May $2019$

$16-$CIV$-$A$4$ GFOTECHNICAL MATERIALS AND ANALYSIS

$($ii$)$ Determine the total shear strength parameters for the tested soil using a suitable

analytical method.

$(10$ marks$)$

$($iii$)$ If a specimen of the same soil were consolidated under an effective confining stress of

$250$kPa $($i$.$e$.{}_3^{\text{'}}=250$kPa $),$ what would be the expected value of principal stress

difference at failure?

$(6$ marks$)$

$($iv$)$ Is the clay normally consolidated or overconsolidated? Give reasons.

$(4$ marks$)$

Hint: Figure below may be useful for this question