Page 249 - Geotechnical Engineering Soil and Foundation Principles and Practice

Pore Water Pressure, Capillary Water, and Frost Action
244 Geotechnical Engineering

11.15. Soil immediately underneath a pavement is 6 ft above the groundwater
table. If the sorption curve for this soil is as shown in Fig. 11.11, what will
be the probable moisture content? Which is more appropriate, the
desorption or adsorption curve? Why?
11.16. At what stage of frost action in the subgrade may it be necessary to
impose a traffic embargo on a road or runway? How long should the
embargo last?
11.17. Under what conditions will rain dry out a soil?
11.18. Name three basic conditions that must exist before ice lenses will grow in a
soil subgrade.
11.19. Describe three principles that may be employed in pavement design to
inhibit the growth of heave-producing ice lenses. Explain how each method
accomplishes its purpose.
11.20. Should ice lenses in soil behind a retaining wall be oriented with their thin
dimensions vertical or horizontal? Explain.
11.21. Explain how freezing an expansive clay can cause it to shrink.
11.22. What minimum foundation depths are recommended to prevent frost
damage in the following cities: Chicago, New York, Denver, Atlanta,
Minneapolis, Los Angeles, Seattle, Phoenix?
11.23. Maximum and minimum recorded daily air temperatures over a 10-day
period are as follows. Predict the depth of freezing: (a) in a clay with a unit
3
3
weight of 14.9 kN/m (95 lb/ft ) and a moisture content of 20%; (b) in a
still lake.

Day 1 2 3 4 5 6 7 8 9 10
Min (8C) 0 14 9 6 20 16 16 10 8 10
Max (8C) 12 2 1 3 12 8 6 2 4 10

11.24. Define and give reasons for permafrost, active zone, oriented lake, pingo.
11.25. What dictates the bottom elevation of permafrost?
11.26. Explain the development and significance of patterned ground.
11.27. A four-story apartment building located on permafrost is sinking into the
ground. Is there any way to prevent further damage to this building?
11.28. Why, when permafrost thaws, does the ground usually settle, and why does
it do so unevenly?
11.29. Suggest two methods to maintain permafrost under a heated building.
How might these methods be modified to also apply to foundations for a
cold-storage warehouse?

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