EVALUATION OF FLEXIBLE PAVEMENT FATIGUE PERFORMANCE BY USING SURFACE CURVATURE INDEX

Abstract

Mechanistic pavement design methods are based on strains calculated at the bottom of the asphalt concrete layer and the top of the subgrade layer. After the pavement construction is complete, only part of the structure reasonably accessible for evaluation is the pavement surface. Surface deflection based test procedures are one of the means available to evaluate the pavement design. The ability of the engineer to check the design performance will therefore be greatly enhanced if a parameter based on surface deflections can be used. Surface Curvature Index (SCI) is a surface deflection parameter. SCI is defined as the maximum surface deflection under a given load minus the deflection measured at the given distance from the center of the load (typically 1-foot). SCI being inversely proportional to the radius of curvature is therefore a measure of tensile strains in the pavement. In this study, the surface deflections were measured by using Falling Weight Deflectometer (FWD). The measured deflections were converted into the surface curvature index. Multiple linear regression analysis was performed on the measured deflections to examine the relationship between the SCI, applied load, and measured asphalt concrete layer temperature. Theoretical relationships were developed between SCI and tensile strains at the bottom of the asphalt concrete layer. Using developed theoretical relationships; the calculated SCI were converted into tensile strains at the bottom of asphalt concrete layer. Comparison between models developed in this study was made with existing models using other surface deflection basin parameters for the prediction of tensile strains. Tensile strains at the bottom of the asphalt concrete layer obtained through calculated SCI were used for the prediction of pavement fatigue performance. Finally, the effect of temperature and load was evaluated on pavement fatigue performance.