Task $3.$ Retaining walls are often found in places where extra support is needed to prevent

the earth from moving downhill. In this case, excavation before putting the retaining wall

can cause cracks in the surrounding properties due to soil settlement or land sliding that can

even cause structural collapse. Your company has been awarded a Design& Build contract

for a mid$-$rise building project. As a civil technician, you are expected to understand the

design and construction details handed over by the design engineer. A geotechnical report

was given to the design engineer for his$/$her analysis. The design engineer designed two

retaining wall systems along the boundaries. The highlighted area of the site was

determined for a $3-$meter excavation. The site location shows the northern, eastern, and

western boundaries which are $18,25,$ and $25$ meters, respectively. Consider the followings

for the cost:

$-$ The prefabricated concrete: $$75\mathrm{.}00$ per cubic meter

$-$ The reinforcement: $$35\mathrm{.}00$ per kg

$-$ The total formwork activities: $$2500\mathrm{.}00$

As the civil technician, you are appointed to propose the cost$-$effective design.

System $1.$ Screw piles

The system includes $6-$meter piles, capping beam, and grout injection in between the piles.

The section area of the capping beam is $450$mm X $550$mm and its required reinforcement

cage weighs $3$ kg per meter of the cage. The interval of piles on the eastern is $2\mathrm{.}5$ meters $($cl

to cl$)$ and on the northern and western boundaries is $2$ meters $($cl to cl$).$ Each pile cost

$$1800\mathrm{.}00,$ and the grout injection requires $20$kg fine cement per square meter for the wall.

The grout work contractor quoted $$5$ per kg including materials to complete the job per

square meter of the boundaries$$ faces. The photos of system $1$ shows the end$-$product and

the site location.

$($Provide your answer in the table shown in the answer sheet$)$

Bill of Quantity$-$ Screw piles

Sr$.$ No Items Unit Quantity Total

Quantity

Rate Amount

Total

System $2.$ secant pile system

This system includes $6-$meter piles with a diameter of $550$mm$,$ a capping beam $(450$mm

height and $550$mm width$),$ and its required reinforcement cage weighing $4$kg per meter. The

concrete piles are to be constructed next to each other with $300$mm intervals, maximum.

$($Provide your answer in the table shown in the answer sheet$)$

Bill of Quantity$-$ Secant piles

Sr$.$ No Items Unit Quantity Total Quantity Rate Amount

Total

Task $4.$ Explain the main stages to implement this project and determine the activities to be

taken at each stage. $$ write down the $($ main stages to implement$)6$ points per each stage

$1.$ desk study$/$brain storming

$2.$ site evaluation$/$ reconnaissance

$3.$ Site preparation

$4.$ Mobilization

$5.$ construction