ELASTIC LAYER ANALYSIS RELATED TO PERFORMANCE IN FLEXIBLE PAVEMENT DESIGN

Based on Ontario experience with flexible pavements and results of the AASHO Road Test, it was found that the calculated subgrade deflection under a standard wheel load is the best indicator of performance of the pavement as a whole, compared with other stress, strain and deformation values calculated by elastic layer theory. In the calculations, layer equivalencies obtained from experience and variations in subgrades were expressed in terms of elastic moduli. It was found that subgrade deflections can be calculated more simply by using Odemark's concept of equivalent layer thickness. Expressions for Load Equivalency Factors were derived from AASHO Road Test data, using this simplified deflection calculation. Finally, a functional relationship between subgrade deflection, number of standard load applications and Present Serviceability Index was established. The findings constitute major parts of a design subsystem to be used within a management system for flexible pavements. It was found that this design subsystem can be linked to experience by comparing calculated subgrade deflections with Benkelman Beam Rebound data, both of which are related to pavement thickness.