$($b$)$ A site with a thick original soil deposit had been reclaimed in the past and the consolidation of this layer is complete. A reclamation fill layer of $15$ m is overlying the original deposit with groundwater table located at the bottom of the reclamation fill. The reclamation fill has a total unit weight of $19k\frac{N}{m^3},$ while the original deposit has a total unit weight of $17k\frac{N}{m^3}.$ A cone penetration test $($CPT$)$ has been carried out using a piezocone at a depth of $20$ m below the ground level and the readings obtained are: $q_c=1$ MPa and $q_t=1\mathrm{.}37$MPa. The piezocone used has a tip resistance correction factor of $0\mathrm{.}58.$ The unit weight of sea water is $10k\frac{N}{m^3}.$

$($i$)$ Classify the original deposit based on the CPT data.

$($ii$)$ The original deposit is found to have settled $1$ m during the consolidation process. The CPT that was carried out before the reclamation at a depth of $6$ m below ground level gave $q_c=0\mathrm{.}2$MPa and $q_t=0\mathrm{.}32$MPa. Assuming the unit weight of soil remained constant during consolidation, calculate the percentage increase in undrained shear strength of the original deposit, if the cone factor, $N_{kt}=14.$

$($iii$)$ Calculate the possible range of measured sleeve friction for the original deposit before the reclamation.

Notes on CPT:

$(9$ Marks$)$

Corrected cone resistance

:$q_t=q_c+(1-a_n)u_2$

:$c_u=\frac{q_t-{}_{v0}}{N_{kt}}$

Undrained shear strength

Soil classification using CPT $($Robertson$,1990,2010)$:

$Q_1=\frac{q_1-{}_{}}{{}_w^{\text{'}}},B_1=\frac{U_2-0}{q_1-{}_{}},F_1=\frac{s}{q_1-{}_w}100\%$

Zone Soll behaviour ives

Senstive, fine grained;

Organic solit$-$peats;

Clays$-$clay to silty clay:

Zone Soll behaviour tree

$4.$ Silt mixtures clayey sill to silty clay

$5.$ Sand mixtures; silty sand to sand silty

$6.$ Sands: clean sands to silly sands

Zone Soll behavlour tree

$7.$ Gravelly sand to sand;

$8.$ Very stiff sand to clayey sand

$9.$ Very stiff line grained

Note: Question No$.4$ continues on page $9.$