$3.$ Consider a $13$ m$.$ deep excavation $(25$ x $40$ m$.)$ in a soil profile which consists of a deep medium$-$stiff $-$ stiff sandy$-$clayey soils $($ cu$=80$ kPa$).(\backslash$gamma dry $=17$ kN$/$m$3,\backslash$gamma sat $=20$ kN$/$m$3).$ The groundwater level is $3$ m below the ground surface. The specification requires the water level to be kept continuously $1$ m$.$ below the excavation base.

a$.$ State alternative retaining structure proposals for this excavation.

b$.$ Select one of the alternatives $($you think the best$)$ and specify the depth of the wall. Calculate the lateral pressures acting on the wall. Use both the theoretical $($Soil mechanics$)$ approach and the empirical formulations by Terzaghi and Peck, Tschebtarioff and Japanese Codes and compare the active thrust for all of these

methods.

c$.$ Give considerations$/$recommendations for base water flow in the case of

i$)$Excavation pit is in a populated area.

ii$)$Excavation pit may be dewatered. $($Specify the total amount of flow into the pit and Safety Factor against piping in this case.$)$

d$.$ For this case, the contractor wants to make ground anchorages for lateral support of the retaining system. Omitting the rigidity and lateral support from the retaining wall itself and thinking that all the lateral pressures will be resisted by the anchorages, make a preliminary anchor design.

i$.$ Select the anchor application pattern $($sh and sv$)$

ii$.$ Select the required # of anchor tendons $($tendons may be $0\mathrm{.}57-$wire strand$)$

iii. Thinking that this system is a permanent retaining system prepare a sketch of an anchor showing all the details for the application drawings.

Solve them with drawing,explaining. Also shown that everything, include every drawing.