To be able to detect seasonal variation trends in the strength of subgrade and other component layers of the pavement system, the influences of temperature and moisture on the resilient characteristics of these materials must be separated and quantified. To this end, an extensive research study was initiated in 1990 to evaluate seasonal changes in the structural adequacy of asphalt concrete pavements within Alberta as measured by surface deflection and/or resilient modulus. Specifically, the objectives of this investigation were to: (a) identify seasonal subgrade temperature and soil matric suction trends, and (b) identify and select suitable strength indices for measuring seasonal variations in pavement response, seasonal variations in pavement response, (c) develop laboratory predictive moduli models in terms of pertinent soil properties through dynamic repeated load testing, and (d) provide guidelines for future implementation of mechanistic-empirical pavement design methodologies. The study consisted of two phases: a field investigation phase and a laboratory testing program. This paper reports on some of the research findings obtained from the field investigation phase. (A)
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