Section B$-$Soil Mechanics

$4.$ A sheet pile wall is to be used to provide a temporary dam as shown in Figure Q$4.$ The wall was driven into an underlying uniform soil profile of permeability $2\mathrm{.}4{10}^{-3}\frac{m}{s}.$ Draw the structure to scale on graph paper and sketch a flow$-$net for the problem. Use your flow$-$net to estimate:

$($a$)$ The seepage rate beneath the sheet pile wall.

$($b$)$ The hydraulic gradient at exit close to the sheet pile wall.

$($c$)$ The factor of safety against quicksand conditions at the excavation floor

$($d$)$ The pore water pressure at point $A$ in the soil.

$($e$)$ If the factor of safety against quicksand conditions at the excavation floor is considered to be too low, suggest possible engineering solutions that could be employed to increase it$,$ whilst still maintaining the depth of the excavation. Use your understanding of flow behaviour to explain why these solutions would work.

Figure Q$4$