Effects of extreme climatic conditions on pavement response

Conventionally it has been presumed that heavy traffic loading is the main driver that causes pavements to reach its limiting performance criteria such as fatigue and permanent deformation, and as a result, pavement designs have primarily only incorporated traffic loading. However, close monitoring of pavements has revealed that in fact, traffic loading alone may not create the conditions that lead to sudden failure of pavements. One aspect that is often not directly included in pavement design is the climatic factors, specifically temperature and moisture variations of the pavement soil. The occurrence of climatic extremes is becoming ever so frequent and there is a pressing need to better understand the effects of these extreme climatic conditions on pavement performance. This study presents the findings of an investigation into the effects of moisture and environmental conditions on the mechanical behaviour of granular pavements. The study was conducted with the aim of determining how seasonal effects from hot and wet climatic conditions impact on the sudden failure of pavements. Data was collected from state-of-the-art instrumentation on two field pavement sites located in Sunshine Coast, Australia. The sites were monitored over three years, and variations in daily temperature, moisture and strain values were analysed. Cyclic strain variations were observed in a cemented pavement basecourse layer where large fatigue tensile strains were present when moisture increased and temperature decreased. The results indicate that as moisture rises and temperature falls, critical fatigue strain increase above the fatigue endurance limit. This occurs when moisture was at or above optimum moisture content and surface layer temperature was between 38°C and 31°C. The data indicated that the change in pore pressure as a result of moisture and temperature variations within the granular basecourse soil were causing the strains in the pavement. Heavy traffic volume only had a minor effect on basecourse strain although the combined effect of soil moisture, temperature and heavy traffic loading was a cause for large fatigue strains in the pavement.