摘要: |
With freezing indexes ranging from 1,200 to over 2,000 deg C-days and frost penetration reaching 3 mm under pavement surface, frost action has always been a major concern for pavement engineers in Quebec, Canada. The province's ministry of transportation has thus undertaken a study on frost action in pavements with two main objectives. The first is to revisit the whole approach of pavement design in severe frost conditions and develop a rational pavement design method to mitigate efficiently the effects of frost action. The second objective is to evaluate alternative techniques that might protect pavement against the detrimental effects of frost action. To gather the data needed to evaluate the performance of different pavement designs in support of those objectives, a specific pavement monitoring program was developed. The modeling and the laboratory work carried out to define the characteristics of the main test site constructed during summer 1994 are described. Mechanical and thermal simulations using ELSYM 5 and a finite element model developed at Laval University have led to an optimal pavement structure for the test site. The benefit of thermal insulation was weighed against the detrimental effect of incorporating a soft layer within the pavement structure to determine the best combination of thickness and depth for the insulation layer. Alternative insulation materials were identified and characterized through a comprehensive laboratory testing program. Based on criteria such as local availability, mechanical and thermal performance, cost, and environmental considerations, three promising materials were selected for the field testing. Saw dust, tire chips, and plastic crumbs were tested and compared with conventional insulated (expanded and extruded polystyrene) and uninsulated pavements. |