Assignment:
Review the report on the blackboard site for the class titled “Improved Performance of Unpaved Roads During Spring Thaw” and answer the following questions about frost issues with roads and spring thaw.
Background:
Frost heave and thaw softening of soils is a major challenge to the stability of structures and infrastructure. In most cases for structures we attempt to locate the bottom of the footing below the frost depth. Maps of frost depth are available for the U.S. and are the basis for the required foundation depth specified in local building codes. For some infrastructure like roads and other surface structures it is not feasible. Therefore, we try to design to minimize the occurrence of frost heave/thaw softening on the performance of the structure/infrastructure.
The report provided is a practical review of trials of a variety of techniques to help ensure satisfactory performance of gravel roads during thaw. You may need to augment this report with some basic internet search of the frost heave process. Be sure to keep track of which resources you found valuable and used for any responses below.
Questions:
1. What is a frost heave and how is it related to an ice lens? Please describe using a computer generated figure that you created if possible. (A picture is worth a thousand words.)
2. What conditions must be present for a frost heave to form? See report p 2
3. Can ice lenses form at temperatures slightly above freezing? Yes, p 2 report
4. If a section of road has been affected by frost heaves, what conceptual strategies might stop the occurrence of future frost heave?
5. Is insulation of the ground against freezing a viable option to reduce frost heave occurrence? (You may want to consult another reference in addition to or instead of the provided report. If you use the report, reference the section that helped you draw your conclusions.) What might you use for insulation?
6. As noted in the report on page 27 or so, did the instrumentation for monitoring performance measure parameters of relevance to frost heave and was any key parameter missed?
7. Referring to table 1 of the report, list your ranking of the techniques most likely to result in improved frost performance?
8. Referring to section 9 of the report compare your expectations from question 7 to the results listed in the table. What techniques that you thought would work did not? Does the report explain the reason to your satisfaction?
9. How much might changing site conditions along the test section of road affect the frost performance observed? Is this addressed in the report? If so, where: list the page.