Assessing Spring Load Restrictions Using Climate Change and Mechanistic-Empirical Distress Models

Nearly 58% of the Manitoba Provincial pavement network is subjected to spring load restrictions, and most of these roads consist of a thin flexible pavement or an asphalt surface treatment. This paper relates pavement deflection data from FWD testing to environmental indices such as the thaw index. Deflection data collected since 1990 on pavement sections and the LTPP site in Manitoba are used to establish network-level and statistically representative values for pavement properties during the thaw weakening and recovery period. The base and subgrade moduli during spring thaw are computed using a back-calculation algorithm and categorized in terms of ranges of the thaw index. The data is used with the prediction models of the AASHTO Mechanistic Empirical Design Guide to assess the impact of spring load restrictions on pavement service life. Five scenarios are considered and these accounted for base conditions on an unrestricted road and for the cases of reducing axle loads, with and without an increase in the number of trips, required to transport a certain payload.