Field Measurement and Modeling of Vertical and Longitudinal Strains from Falling Weight Deflectometer Testing

Abstract

This study investigates longitudinal tensile and vertical compressive strains at the bottom of the hot mix asphalt (HMA) layer subjected to a falling weight deflectometer during different seasons at the fully instrumented Integrated Road Research Facility located in Edmonton, Alberta, Canada. First, dynamic strain pulses were measured and characterized with respect to their shapes and durations. Also, the impact of the HMA layer temperature in different seasons on the in situ measured strains was evaluated, and strong relationships between peak strain values and temperature were found. Second, some well-established analysis packages were used to predict the measured responses based on the backcalculated and laboratory-determined moduli. Finally, by using the bottom-up fatigue cracking and rut depth prediction models, the impact of strain prediction error on the estimated performance was also evaluated. Through comparison of predicted and measured strains, it was found that on average the potential fatigue life can be overestimated by 1.7 times, whereas the potential rut depth of HMA is less affected, overestimated by 1.2 times based on the three software programs used.