A finite element analysis of pavement freezing and thawing was performed on four flexible pavement structures developed to representtypical pavements that receive spring load restrictions because of thaw weakening. The pavement structures consisted of 2- and 4-in.-Thick asphalt concrete surface courses, 6- and 12-in.-Thick granular base courses and fine- and coarse-grained subgrade materials. Tdhc, atwo-dimensional finite element heat transfer model, was used for the analysis. Air temperatures, short- and longwave radiation, and convection were included as the external variables driving the pavementthermal response. Latent heat caused by the phase change of water during freezing and thawing, is included in the model. The results suggest that average daily pavemnt surface-air temperature differences vary from 2 deg f in february to 11 deg f in may. These data suggest that pavement thawing will be initiated during this time for average daily air temperatures of 30 deg f or less. In addition, it was found for the pavements analyzed that thawing reached the top of thesubgrade, after pavement surface temperatures reached 32 deg f, in 1 to 4 days in thin pavements and in 4 to 9 days in thick pavements.The duration of thawing for total thawing to occur was correlated with the freezing index for all subgrade types combined with satisfactory results. This paper appears in transportation research record no. 1286, Design and evaluation of rigid and flexible pavements 1990.
Samenvatting