Q$5)(20\%)$

A $9-$m high mechanically stabilized earth retaining wall with galvanized steel strip

reinforcement in a granular backfill was constructed. Granular backfill has unit weight of $20$

$k\frac{N}{m^3}$ and $c^{\text{'}}=0,{}^{\text{'}}=36.$ Information about galvanized steel reinforcement: width of the strips

$7\mathrm{.}5cm,$ vertical spacing $60cm,$ horizontal spacing $90cm,$ yield strength of strip $240$MPa, and

soil$-$strip friction angle $20,$ strip thickness $5mm,$ strip length $12m($constant strip length is

used$).$ Corrosion rate of galvanized steel strip is $0\mathrm{.}025m\frac{m}{y}$ear and the life span of the structure

is $50$ years. The first strip is placed at $30cm$ below the top of the wall, the lowest strip is placed

at $30cm$ above the base of the wall.

a$)$ Check whether the thickness and length of the strips are sufficient for satisfying factor

of safety of $3\mathrm{.}0$ against tie break and pullout. If they are not sufficient, determine the

new thickness and length to satisfy required F$.$S values.

b$)$ If you were to use different lengths of strips at different depths, calculate the lengths

you would use for the $1^{st},5^{t^{th}},{10}^{th}$ and ${15}^{th}$ strips from the top of the wall.

c$)$ Comment on how you would incorporate in calculating factor of safety against tie break

and pull out, the effect of a surcharge load $(q,$kPa $)$ placed at the ground surface of the

wall. Sketch the problem, write the equations for F$.$S$.$ and comment in a few sentences

about where in the equations you will incorporate some changes. You do not need to

make calculations.

d$)$ Part $($d$)$ is a separate $/$ independent question than other parts. The following figure is

taken from the summer practice report of a METU CE student $($summer $2020),$ showing

a mechanically stabilized earth wall construction in Ankara. Discuss in a few sentences,

what do you see in the figure, do you expect any problems, if so what could be the

problems$/$effects$.$