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3. Excavation and retaining structure

The excavation depth for the foundation level of the administrative building was

about 5 m, two equipments were used which are excavator and loader. The first step

was marking the excavation area and that was done by a surveyor using a total

station.

The excavator used was a hydraulic excavator (backhoe), the excavator achieved

its work by choosing a suitable standing position and then it began digging in the soil

of the excavation area by pulling the dipper back toward the machine and when it

was loaded with excavated soil, the excavator boom was raised and the excavator

body rotated while maintaining the track in its position to load the trucks if they are

available or to collect excavated soil in one place to be loaded to the trucks using a

loader. After excavating to a depth of 2m, the excavator changed its position and

began digging again to a depth of 2m in its new position, and that was repeated until

all the area was excavated to this level. After that the excavator changed its positionand stand at the new excavated level which is 2m lower than the first standing

position, then the excavation was completed to the required level as mentioned

before. Figure 1 shows the process of excavation using an excavator.

A loader was used to load the trucks with the excavated soil that was collected

by the excavator, it also made a ramp to the excavated area and assisted the

excavator in the excavation process, it was also used for grading and leveling.

Three offroad dump trucks were used to transport the excavated materials from

the site to the dump area which was 10 km away from the site.

Figure 1

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y One side of the excavation required a retaining structure, so the areasurrounded this side was not excavated until the retaining structure was

installed.

Retaining structure

Bored piles were used to support the excavation side and prevent it from failure, the

pile length was 10m, its diameter was 0.6m, and its reinforcement was 8 25 for the

main reinforcement and the stirrups were 7 8 /m. The steps of forming these piles

are as follows:

1. Site preparation and delivering equipments to site.2. Marking out the position of piles, 10 cm was left between each pile and the

adjacent pile.

3. Preparation and formation of the steel cage (the pile reinforcement).4. A special machine was used in drilling, it pushed a casing down to a depth of

2m and it removed the soil within the casing, then it completed pushing the

casing to the next 2m and removing the soil within the casing, this process

continued until reaching the required depth.

5. Installation of the steel cage in the borehole.6. Concrete was poured in the borehole to form the bored pile.7. Casing was removed.8. The next pile that was bored was not the adjacent pile to the finished pile

but it was the one next to it, the piles were casted in a sequence as shown in

figure 2 where the number written on each pile represents the order of

casting this pile.9. A 0.6m x 0.6m beam was casted on the top of the piles to connect them

together, the reinforcement of this beam was 6 16 in the top and in the

bottom.

10.The excavation process was then completed safely in this area.Figure 2

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