Flexible pavement overlay design by dynamic deflections - phase II

This report summarizes a comprehensive study to develop a flexible pavement overlay design procedure based on Falling Weight Deflectometer (FWD) deflections for the South Carolina Department of Highways and Public Transportation (SCDHPT). The study included the establishment of 16 permanent pavement test sections located throughout South Carolina. At these test sections, bimonthly FWD testing was performed to develop a substantial data base of FWD deflection basins. A recommended flexible pavement overlay design procedure was developed. The procedure utilizes FWD deflections to backcalculate in situ subgrade modulus and composite pavement stiffness. The procedure is based on 1986 AASHTO Guide NDT - Method 2 procedures, but includes revised techniques for determining subgrade modulus and performing temperature corrections for asphaltic materials. The proposed flexible pavement overlay design procedure is shown to provide reasonable and consistent results.