Dewatering Recap

In an effluent stream reach, where does the water flow?

• From the stream to groundwater

• From groundwater to the stream

• From the ocean to the stream

• From the stream to the ocean

What is one purpose of lowering the water table or groundwater control in excavation?

• To increase the water content in the soil

• To provide a suitable working surface at the bottom of the excavation

• To enhance the growth of vegetation

• To increase the temperature of the soil

What is the effect of soil boiling or piping on soil at the bottom of an excavation?

• Increases soil strength

• Reduces the bearing capacity and stability of soil

• Decreases permeability

• Reduces seepage

Which method involves lowering the water table in advance of excavation?

• Sump/Open Pumping

• Water cut-off

• Pre-drainage

• Ground freezing

Which method involves the use of grout in construction excavations?

• Sump/Open Pumping

• Pre-drainage

• Water cut-off

• Ground freezing

What does 'Δh' represent in the seepage formula?

• Total hydraulic head difference

• Number of flow channels

• Number of equipotential drops

• Flow rate

What is the purpose of a flow net in seepage analysis?

• To measure the hydraulic conductivity

• To visualise flow lines and equipotential lines

• To calculate soil density

• To determine the pore water pressure

What is the hydraulic head difference represented by in the seepage formula?

• Δh

• Nf

• Nd

• q

An ideal granular filter must : (multichoice)

• Ensure soil retention

• Ensure adequate drainage

• Ensure materials can segregate

• Ensure materials have apparent cohesion

Sum pumping is favourable near large drawdown or near to confined aquifers

• True

• False