Use a separate answer book for this part, answer all four questions.

$1.$

a$.)$ The retaining wall shown in Figure Q$1$ retains a homogeneous soil with a coefficient of permeability $k=3{10}^{-6}\frac{m}{sec}.$ What is the daily flow $($in $m^3)$ out of the drainage holes at the base of the wall, that are spaced $2\mathrm{.}5m$ apart, if rain generates a constantly wet surface on the ground behind the wall? List the various boundary conditions to the flow net that you establish and any other considerations that you think are important.

$(12$ marks$)$

b$.)$ Calculate the pore water pressure and the vertical effective stress at a point halfway down the back of the wall if the bulk unit weight of the retained soil is $20k\frac{N}{m^3}.$

$(4$ marks$)$

c$.)$ What would the long$-$term pore water pressure be at the same point, halfway down the back of the wall, if the drainage holes became blocked?

$(2$ marks$)$

d$.)$ In addition to the drainage holes, how might you facilitate drainage at the back of the wall?

$(2$ marks$)$

Figure Q$1$