Q$1.($a$)$ A field compaction control test was conducted on a compacted fill. The mass of the material removed from the hole was $1800g$ and the volume of the hole was found to be $900c{m}^3.$ A small sample of the soil lost $16g$ in the drying test and the mass remaining after drying was $100g.$ The laboratory control test results are shown in the figure. $(30\%)($i$)$ If end$-$product specification requires $95\%$ relative compaction and $=($optimum $-1\%)$ to $($optimum $+1\%),$ determine the acceptability of the field

compaction and state why this is so$.$

$($ii$)$ If it is not acceptable, what should be done to improve the compaction so

that it will meet the specification?

Fig. Laboratory compaction curve$($b$)$ An embankment will be constructed to have a final volume of $4,5x0m^3(x$ is the

last digit of your student number$).$ From the Standard Proctor test, the maximum dry

density and the optimum moisture content of the fill is $1900k\frac{g}{m^3}$ and $12\%$ respectively.

The bulk density and moisture content of the soil at the borrow area are $1500k\frac{g}{m^3}$ and

$10\mathrm{.}5\%.$ The Relative Compaction required is referred to that for the "fill material"

described in the General Specification for civil engineering, clause $6\mathrm{.}48.$

Estimate the cost of excavation if the cost is $$20$ per $m^3.($Assume the cost is based

solely on the volume of the soil excavated from the borrow area$).$

Q$.2$ A site is underlain by a layer of normally consolidated clay $6m$ thick. In order to

minimize settlement, a pre$-$loading pressure is used to pre$-$load this site. The

average effective overburden pressure at the middle of the clay layer at present is

$100$kPa. The increase of pressure due to the permanent design load for the site is

$120$kPa. The clay is bounded by a layer of sand above and impermeable layer

below. The other parameters of the clay are given below:

$($a$)$ Determine the time in months required to load the site if primary consolidated

settlement is to be eliminated for a given total pre$-$compression pressure of

$200$kPa,

$($b$)$ If the pre$-$compression cannot be completed in $9$ months, provide vertical

drains, together with the preloading, to speed up the consolidation such that only

$9$ months of preloading is allowed. Assume $C_V=C_r.$ Radius of sand drain to be

$100mm.$ Using the same preloading pressure, design the optimal spacing of the

vertical drain.