Topic 2 Excavation and Construction Dewatering

To conduct subsurface construction work, the earth has to be excavated and it is important to consider surrounding movements. To hold the ground surface against topple, what is needed to be installed?

• ground water

• ground mixer

• ground support

For shallow excavation of dry sand and clay for a long-term stability, it can be acceptable to leave certain safe slope to prevent the sides of the ground against topple. The angle of the slope shall be _______.

• equal to the angle of friction of the soil

• equal to half of the angle of friction of the soil

For a large excavation, select one or more reason(s) for it to be infeasible/unsuitable to provide just a safe slope along side wall.

• too large span

• expensive

• consume time

For ground support installation, which of the following is the general way for sands and silts?

• the sheeting is driven up to the excavation level, then lateral bracing is connected as excavation proceeds with depth

• the sheeting is driven to a depth below the excavation level, then lateral bracing is connected as excavation proceeds with depth

For ground support installation, which of the following is the general way for stiff clay and weak rocks?

• the sheeting is driven to a depth below the excavation level, then lateral bracing is connected as excavation proceeds with depth

• the sheeting is installed in open or partially completed excavation to a depth below the excavation level, then lateral bracing is connected

• the sheeting is installed in open or partially completed excavation up to the excavation level, then lateral bracing is connected

Construction Dewatering means to keep the excavated area ____.

• Dry

• Wet

• Partially Wet/Dry

Select the dewatering process suitable for shallow excavation and water table up to a depth of 1 m.

• Ditches and sumps

• Well-points

• Vacuum Dewatering

• Deep-well Pump

Select the dewatering process suitable for excavating water table up to a depth of 7 m for coarse soil.

• Ditches and sumps

• Well-points

• Vacuum Dewatering

• Deep-well Pump

Select the dewatering process suitable for excavating water table up to a depth of 20 m for coarse soil.

• Ditches and sumps

• Well-points

• Vacuum Dewatering

• Deep-well Pump

Select the dewatering process suitable for excavating water table up to a depth of 5 m for silts.

• Ditches and sumps

• Well-points

• Vacuum Dewatering

• Deep-well Pump