Investigation of Atmospheric Impacts on Spring Load Restriction Limits Imposed by State Transportation Agencies (05-2699)
Jennifer Hanson, University of North Dakota

Freezing and thawing of subsurface soils is a common occurrence in cold regions. This process results in hundreds of millions of dollars of damage to roadways in the United States every year. As springtime thawing takes place, the weakened roadbeds are susceptible to damage caused by vehicles carrying heavy loads due to water in the soils trapped between the road surface and the frozen subsurface. State departments of transportation attempt to mitigate damage by placing load restrictions on roads prone to this problem. The major issue with placing load restrictions is knowing the right time to put them into place such that impact to commercial traffic is minimized while the structural integrity of the roadway is maintained. This research focused on a method to better determine when spring load restrictions should be enacted. This was done using an integrated climatic model driven solely by atmospheric conditions to model soil conditions. The model was initialized using Global Forecast System 384-hour model output, pavement temperatures, subsurface temperatures, pavement and subgrade profiles, and subsoil types and properties. Subsurface temperatures were obtained from subsurface temperature probes equipped with sensors that have been installed in roadbeds at six locations across the state of North Dakota. Model results were verified against observed subsurface temperatures. The goal of this research was to determine the benefits of using such a modeling system and to identify situations in which this system performs well and/or poorly.