Spatial and temporal freeze-thaw variations in Alaskan roads

摘要

Seasonal freeze and thaw impact a road's ability to bear loads. Temperature index models are one of the methods being used to manage seasonal weight restrictions on roads. Many of these methods are limited to specific regions in which they have been calibrated and more universally applicable models are sought. We conducted a mull-year study of road subsurface temperature data in Alaska to understand temperature variations among stations and support the development of generally applicable models. Time-stability analysis showed that stations located within 25 km had consistent temperatures with the consistency increasing with measurement depth. At greater separation distances, stations' relative cold or warm biases were maintained across years. Up to 95% of temperature differences among stations was explained by latitude when linear regression was used. Temperature time series showed distinct isothermal conditions in spring at temperature below 0 degrees C. For stations located further south, thaw penetration rates were greater, and surface n-Factors varied more. A constant thawing index was also tested to determine thaw dates. Thaw depths corresponding to these dates were relatively consistent for northern stations but varied substantially for southern stations.