Monitoring of Flexible Pavement Structures during Freezing and Thawing

摘要

The structural behavior of flexible pavement in cold regions is greatly affected by environmental factors and traffic loads. The main objective of this study was to better understand the response of pavement structures during thawing and to better predict the loss and recovery of the bearing capacity as a function of the evolution of the thaw and temperature in the pavement. Two identical test sections were used; one was built in the geotechnical laboratory of Laval University and one was located at the Laval University Road Experimental Site (SERUL). Each layer of the tested sections was instrumented with strain, stress, moisture, and temperature sensors. In the laboratory, a heavy vehicle and environmental simulator, which can control the air temperature on the pavement surface, was used to apply real traffic loads and control temperature. A temperature of -10°C was used for freezing, and a temperature of 10°C was used for thawing. The carriage speed was set a 5 km/h, the tire pressure was set at 700 kPa, and loads of 5000, 5500, and 4000 kg were tested to simulate standard, winter premium, and spring load restriction conditions. At the SERUL, a falling weight deflectometer (FWD) was used to simulate heavy loads. The results indicate that the freezing of a given structural layer reduces the strains and stresses in the layer, as well as in the underlying layers. After one freeze-thaw cycle, the reduced moduli in unbound materials indicate that some damage occurs during freezing and thawing. Also, strain increases significantly when the thaw front penetrates into the pavement and at the beginning of summer when the rise of temperature reduces the stiffness of the asphalt concrete layer. Finally, we noticed that, during freezing, a 10% load increase induces a 10% increase of strain and stress in the pavement structure.