Prompted by the continuing frost damage experienced throughout Pennsylvania, the Pennsylvania Department of Transportation, Bureau of Materials, Testing and Research initiated a research project in 1969 to evaluate the frost problem in the State. This research project deals primarily with statistically analyzing freezing index variation, frost depth prediction techniques and ensuring appropriate frost design changes. Data for these analyses are available from 14 field test sites across Pennsylvania which have been monitored monthly throughout the last 8 freezing seasons. Frost depths predicted by two theoretical methods and one empirical method are statistically regressed with actual maximum frost depths at the field sites. The sensitivity of the prediction to variations in the pertinent dependent variables are also considered. The best prediction technique for the Pennsylvania data set is chosen, and comments on obtaining realistic input variables are made. Measurements of the effects of the effects of differential heaving of the pavement system and of loss of subgrade bearing support capacity during the spring thaw period are tabulated. Normalized pavement surface deflection measurements made with a Road Rater are used to indicate seasonal changes in subgrade support. Surface heave measurements made with standard engineering survey levelling equipment are referenced to a "frost free" bench mark. Appropriate frost design changes are recommended as a result of the findings from the field test site data and from the Penn State Test Track research. An optimum thickness of subbase or replacement material for frost susceptible subgrade soil is suggested. The increase tht the subbase material provides to the overall pavement system strength or stability is weighed against the increase in total frost depth penetration below the pavement surface. A method of estimating springtime subgrade support reductions for a given highway location is recommended along with suggested pavement system layer design procedures which consider these probable seasonal support losses. (FHWA)

  • Corporate Authors:

    Missouri State Highway Department

    Division of Materials and Research, State Highway Building
    Jefferson City, MO  United States  65101

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590
  • Publication Date: 1979-5

Media Info

  • Pagination: 268 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00316392
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-PA-RD-68-30-2 Final Rpt., FCP 45C2-222
  • Contract Numbers: 68-30
  • Files: TRIS, USDOT
  • Created Date: Dec 30 1980 12:00AM