Spring Load Restriction Modeling

Freezing and thawing of subsurface soils is a common occurrence in cold regions. This results in hundreds of millions of dollars in damage to roadways in the United State every year. As springtime thawing takes place, the weakened roadbeds are susceptible to damage caused by vehicles carrying heavy loads due to water 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 main concern in placing load restrictions is recognizing the right time to implement restrictions such that the 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 coupling an integrated climatic model, known as the Enhanced Integrated Climatic Model (EICM), driven by observed atmospheric conditions, 240-hour Global Forecasting System (GFS) model output, and 384-hour GFS model output to model soil conditions. The results of the EICM were compared to the observed subsurface temperatures obtained from the site that was modeled.

This paper summarizes and presents the research results of winter 2004-05 field trials. These results showed that the EICM can be successfully coupled with an atmospheric model to predict subsurface conditions up to fifteen days in advance. The paper also identifies difficulties encountered in using long-range numerical weather prediction models without the use of proper EICM background condition initialization. A description of how these problems were resolved is described. The final section of the paper describes the promise of this method as an effective operation decision support tool for specifying when to place spring load restrictions.