QUESTION $4.$

A well$-$sealed sheet pile wall has been installed partially through a silty sand layer, as shown in

Figure Q$4.$ Assume a sheet pile $12m$ long penetrates $6m($halfway$)$ into the silty sand layer of

thickness $12m.$ For this condition:

$($a$)$ Draw a flow net using three $($or four at most$)$ flow channels.

$($b$)$ If the water height on the upstream side is $5m$ and on the downstream side $1m,$ compute the

amount of water flowing under the sheet pile per metre of wall if the coefficient of permeability

is $3\mathrm{.}1{10}^{-4}c\frac{m}{s}.$

Figure Q$4$ Cross$-$section of a sheet pile installed in a silty sand soil layer

$($c$)$ Compute the total head, pressure head, and elevation head for a point halfway up the sheet

pile from its base, on either side of the sheet pile. Assume the datum is at the bottom of the

silty sand layer.

$($d$)$ Discuss the significance of seepage control for civil and environmental engineering, both

generally and specifically in the context of the current climate emergency, such as from the

aspect of water resources and energy conservation.

Figure Q$4$ Cross$-$section of a sheet pile installed in a silty sand soil layer