GEOTECHNICAL ENGINEERING EXAM 2 QUESTIONS AND ANSWERS ALREADY PASSED
What is a flow net? How is it drawn? Explain the difference between flow lines and equipotential
lines in your answer. - Answers A flow net it used to calculate seepage before software. It
consists of two sets of perpendicular lines that create a curvilinear grid. Lines that connect
equal pressure are drawn, and flow lines are drawn perpendicular and form squares.The flow
line is the predicted path that water follows. The equipotential lines connect points of equal
pressure (or head).
What do engineers do to calculate Darcy's law (seepage) in two dimensions? - Answers
Engineers use software that simulate ground water flowing down.This use to be done with flow
nets, but they are less accurate and take longer.
Explain why piping failures occur rapidly based on the loss of material. - Answers Soil has
friction. Water gets in between particles and undoes the friction. As soil iscarried away, the
seepage path gets shorter, so the gradient goes up. The increasing seepage creates more
erosion.
Explain the critical zone - Answers The permeable layer retains water, and this water moves
downward. Once the water reaches the bottom of the sheet pile, there is a critical zone where
there is no stress, and the strength decreases. Water then flows up the other side and brings
particles with it to cause failure.
Which type of geosynthetic is most likely to be composed of expanded polystyrene? - Answers
geofoam
Which of the following is a primary issue that must be addressed in the design of a geosynthetic
filter? - Answers Clogging
The typical application of geonet is filtration. - Answers false, it's typically used for drainage
Which of the following defines permittivity? - Answers k/t
Transmissivity is the in-plane permeability of a geosynthetic. - Answers true
Which of the following is a typical application for a non-woven geotextile? - Answers Nonwoven
geotextiles are often used for filtration, and protection (e.g., against erosion).
Which type of geosynthetic is most likely to be used to reinforce soil for a mechanically
stabilized earth retaining wall? - Answers geogrid
If a particular geonet is used as a drain beneath 20 ft of fill, it will have the same transmissivity
as the same geonet used as a drain beneath 5 ft of the same fill. - Answers The geonet under 20
ft of fill experiences a higher stress, or pressure than the geonet under 5 ft of fill. The high
stress means the transmissivity should be less beneath 20 ft of fill compared to 5 ft of fill.
What is a flow net? How is it drawn? Explain the difference between flow lines and equipotential
lines in your answer. - Answers A flow net it used to calculate seepage before software. It
consists of two sets of perpendicular lines that create a curvilinear grid. Lines that connect
equal pressure are drawn, and flow lines are drawn perpendicular and form squares.The flow
line is the predicted path that water follows. The equipotential lines connect points of equal
pressure (or head).
What do engineers do to calculate Darcy's law (seepage) in two dimensions? - Answers
Engineers use software that simulate ground water flowing down.This use to be done with flow
nets, but they are less accurate and take longer.
Explain why piping failures occur rapidly based on the loss of material. - Answers Soil has
friction. Water gets in between particles and undoes the friction. As soil iscarried away, the
seepage path gets shorter, so the gradient goes up. The increasing seepage creates more
erosion.
Explain the critical zone - Answers The permeable layer retains water, and this water moves
downward. Once the water reaches the bottom of the sheet pile, there is a critical zone where
there is no stress, and the strength decreases. Water then flows up the other side and brings
particles with it to cause failure.
Which type of geosynthetic is most likely to be composed of expanded polystyrene? - Answers
geofoam
Which of the following is a primary issue that must be addressed in the design of a geosynthetic
filter? - Answers Clogging
The typical application of geonet is filtration. - Answers false, it's typically used for drainage
Which of the following defines permittivity? - Answers k/t
Transmissivity is the in-plane permeability of a geosynthetic. - Answers true
Which of the following is a typical application for a non-woven geotextile? - Answers Nonwoven
geotextiles are often used for filtration, and protection (e.g., against erosion).
Which type of geosynthetic is most likely to be used to reinforce soil for a mechanically
stabilized earth retaining wall? - Answers geogrid
If a particular geonet is used as a drain beneath 20 ft of fill, it will have the same transmissivity
as the same geonet used as a drain beneath 5 ft of the same fill. - Answers The geonet under 20
ft of fill experiences a higher stress, or pressure than the geonet under 5 ft of fill. The high
stress means the transmissivity should be less beneath 20 ft of fill compared to 5 ft of fill.
