YOU MUST DO BIII AS ITS IMPORTANT Question $3$

$($a$)$ Discuss the difference in the applicability of the constant$-$head and falling$-$head tests in measuring soil permeability. Explain the causes for the difference.

$(6)$

$($b$)$ The dimensions of a dam are shown in Figure Q$3.$ The coefficient of permeability of the permeable soil layer is $4{10}^{-5}\frac{m}{s}.$

i$)$ Sketch a flow net for flow through the permeable layer and calculate the quantity of seepage in $m^3$ per day per metre.

ii$)$ Calculate the hydraulic uplift force at the base of the dam per metre length along the axis of the dam.

iii$)$ Discuss the effect of the seepage on the soil at the downstream $($exit$)$ side.

$(8)$

iv$)$ Discuss possible measures that can be taken to reduce the exit hydraulic gradient.

$(4)$

$(4)$

Figure Q$3$