The following data $($Table $1)$ was obtained from a $24-$hour maintained load

oedometer test on a sample of estuarine clay $/$ silt which was taken from a depth of $4$

$m$ at the proposed Dargle River Crossing site in Bray, Co$.$ Wicklow, as shown on

Figure $1.$

Table $1$

Dense gravel

Figure $1$

$($a$)$ Determine the values of the preconsolidation pressure $(P_p^{\text{'}}),$ compression

index $(C_c)$ and recompression index $(C_r)$ from the oedometer test data;

$($b$)$ Determine the overconsolidation ratio $($OCR$)$;

$($c$)$ Using the chart shown on Figure $2$ below $($from Lambe and Whitman, $1979),$

check that the value of $C_c$ is sensible$.$ Note $e_0$ is the initial void ratio. Figure $2$

$($d$)$ Estimate the likely primary consolidation $()$ due to the load imposed by the

proposed embankment.

Use the formula:

$\frac{}{H}=\frac{C_c}{1+e_0}[log(\frac{{(}^{{}_{v0}})+({}_v^{\text{'}})}{{}_{v0}^{\text{'}}})]$

where:

$C$ is the appropriate compression $/$ recompression index

${}_{v{0}^{\text{'}}}=$ initial in situ vertical effective stress

$v{0}^{\text{'}}=$ change in vertical effective stress