$2\mathrm{.}4$ The section through a sheet pile wall along a tidal estuary is given below. At low tide the water

level in front of the wall is at ground surface; the water table behind the wall lags $5m$ behind

tidal level. The partial flow channel is estimated at one$-$tenth of the full channel. Soil has a

saturated unit weight of $17k\frac{N}{m^3},($i$)$ Compute the factor of safety against heaving, $($ii$)$ Compute

the factor of safety against boiling, $($iii$)$ What would be the unit weight of backfill to the level of

back wall ground surface that will result into a factor of safety against heaving of $2?[($i$)=1\mathrm{.}6,$

$($ii$)=1\mathrm{.}7,($iii$)=1\mathrm{.}9k\frac{N}{m^3}]$