Assessment of thaw weakening in pavement stiffness using the spectral analysis of surface waves

Abstract

Mechanistic methods for the design of pavement structure in cold regions require an adequate knowledge of the seasonal variations in elastic properties of the structural layers. In this study, the spectral analysis of surface waves (SASW) method was adopted to monitor the changes of the stiffness modulus in pavement during a complete freeze–thaw cycle. The SASW tests were performed on a section of pavement in Québec City over a complete freeze–thaw cycle in 2001. The stiffness profiles of the pavement layers were back-calculated from the experimental dispersion curves using a forward-modelling approach based on a discrete stiffness matrix method. The seasonal variations in stiffness in the base, subbase, and subgrade were then assessed. The thaw-weakening period and the recovery in stiffness after the complete thaw were observed. The minimum value of the stiffness modulus in the base layer was about 80% of its prefreezing value, and those of the subbase and subgrade were about 60%. A sharp change in the back-calculated moduli at temperatures close to the freezing point was observed. The relevance of using the SASW method to study the thaw weakening and recovery in pavement stiffness affected by freeze–thaw cycles is clearly shown in this study.Key words: SASW, pavement, seasonal variation, stiffness, thawing, recovery.