Thawing, Field Study, Canada

In cold climates, and with frost susceptible materials, freeze thaw phenomena play a major role in pavement deterioration. Figure 8.8 shows examples of measurements of deflection development, and of water content in the subgrade, performed in a full scale experiment, carried out in Quebec (Savard et al., 2005). The pavement structure consists of 18 cm of bituminous materials over a granular base (40 cm) and a 40 cm thick sand frost-protection layer. The pavement is subjected to frost indices exceeding 1000°C. days. The deep frost penetration (up to 1.5 m during severe win­ters) leads to large water content variations in the silty, frost susceptible subgrade,

which considerably affect the pavement deflections. The period of reduced bearing capacity lasts about 2 months (thaw period, followed by a recovery period, where the excess moisture dissipates).