e. Again holding the cup, slowly pour the entire 225 ml of water into
the pie pan around the outside of the cup and sand.
f. Observe what happens and record the time it takes for the soil to
reach saturation.
g. Once the soil is saturated, one student win hold the cup firmly in
place while the other gives the side of the cup several sharp taps to
simulate earthquake shaking. Observe what happens to the weight.
C. Conclusion
Help students to clean up and then initiate the discussion. Ask: If the
weight in our experiment were an occupied building, and liquefaction
occurred over a large inhabited area, as it did in the San Francisco Bay
Area in 1989, what would be the effect on:
Q
People?
Q
Private homes?
Q
Schools?
Q
Buried lifelines (gas, water, electrical, oil, sewage)?
Q
Agricultural lands?
Q
Medical facilities, fire stations, police stations?
Q
Large urban areas (Memphis, San Francisco, Boston)?
Q
Industrial areas?
Q
Materials that had been discarded in old sand boils? (These could
range from dead cows to old refrigerators to poisonous waste.)
ADA P T A T I ON S AND E X T E N S I ON S
1. Make sand of various particle sizes and objects of different masses
available for student experiments. Investigate the degree of
liquefaction each will exhibit and the effects on the structures that rest
upon them. (A layer of diatomaceous earth under the sand will bubble
up when the table is rapped. Try it!)
2. Invite students to find ways to vary the amount of force they apply
to the sand and water mix in the model.
3. Provide an aquarium or plastic gallon jars so students can
experiment with larger models. Use transparent containers of any
size—even a plastic sandwich box—for an interesting side view.
4. Bury objects in the sand and observe the results.
5. Develop models of overhead power lines, pipelines, sewage lines,
light posts, and highways, and observe how liquefaction affects them.
6. Challenge students with this question: If a building has already been
constructed on soil that has a potential to liquefy, what can be done to
reduce the likelihood of damage? Invite them to design and test model
structures that would reduce structural damage during liquefaction.
A G U
/
F E M A
91
S
E I S M I C
S
L E U T H S
