SEASONAL VARIATIONS IN PAVEMENT STRENGTH

In regions subjected to severe frost, spring thaw and the corresponding reduction in subgrade strength can pose significant problems for pavement structural capacity. A large portion of the annual pavement fatigue occurs during the spring thaw when the pavement is in its weakest state from a support perspective. The magnitude of pavement damage varies with the amount of thawing, type of subgrade, and loads applied. An investigation into the effects of seasonal variations in pavement response to loading has been completed for a series of test sections in southern Ontario, Canada, by monitoring variations in the pavement deflection and subgrade modulus values from Falling Weight Deflectometer (DFW) tests. The key pavement layer response indicators such as normalized dynamic deflection, subgrade modulus, subgrade deflection, and vertical compressive strain were calculated using the MTO PROBE pavement layer analysis program. By charting the variations in these key pavement response indicators throughout the traditional spring thaw period, and comparing them to the measurements taken during the previous fall, a series of environmental factors affecting pavement performance and response has been developed.