Investigation of Thermally and Mechanically Balanced Structural Design of Insulated Pavements for Cold Region Applications

Adding an insulation layer above the frost-susceptible layer in regular pavement structures was proved to be an efficient way to mitigate the influence of climates, such as frost heave and thaw weakening, on pavements in cold regions. However, there is limited research in the area of insulated pavement performance evaluation and design procedures. To bridge the gap and design the structure of insulated pavements, we developed an approach that integrated the selection of the failure criteria, the generation of a trial structure, the evaluation of the thermal and mechanical responses based on a finite-element (FE) model, and the prediction of the pavement rutting and cracking performance. To calibrate the heat transfer process and the thermal field of the FE model, four large-scale pavement boxes were constructed, with one as the control box (no insulation layer) and three others insulated by extruded polystyrene (XPS) boards, tire chips, and foamed concrete, respectively. The spatiotemporal variations of temperature distributions in each box using thermocouples were monitored, and the thermal properties of the insulation materials were back-calculated by a simulated annealing method. Based on the mechanical and thermal responses of various insulated pavements, we calculated the maximum axle load repetitions and developed a sample design table for insulated pavements. The design table indicates that the pavements insulated by XPS boards and foamed concrete can bear more load repetitions than uninsulated pavements, while the tire chips insulated pavement can bear more traffic repetitions only when the overlay thickness is greater than 35 cm. The temperature of the subgrade layer in the insulated pavements is more stable than that in the uninsulated pavements, and a thicker insulation layer results in less temperature variation in the subgrade layer. This study provides new insights into the behavior of insulation layers under cold temperature conditions and helps guide the design of insulated pavements in cold regions.