CAIT project no.: 220 RU7288
Fiscal Year: 2007/2008
Rutgers-CAIT Author(s): Nenad Gucunski
External Author(s): Vincent Nichnadowicz
Sponsor(s): NJDOT, FHWA-USDOT
For rehabilitation design processes, the new Mechanistic-Empirical Pavement Design Guide (MEPDG) relies heavily on the material stiffness backcalculated from the deflection measurements taken from existing pavements. These measurements are typically made using Falling Weight Deflectometer (FWD) or Heavy Weight Deflectometer (HWD) units. In order to provide high quality and consistent material stiffness data for the MEPDG, the New Jersey Department of Transportation (NJDOT) wishes to develop an FWD Procedures Manual that will regulate field testing, analysis, and reporting procedures for FWD and HWD equipment. Adherence to the developed procedures during FWD testing and analysis, whether by State personnel or private contractors, should ensure that good quality material stiffness values are input into the MEPDG processes.
This project sought to examine the state-of-practice in FWD testing and analysis procedures by looking at the standard protocols of a number of other highway agencies. The specific needs of NJDOT were also examined and a protocol was developed that encompassed current standard practice in a way most suited to NJDOT operations. This report documents the development of the FWD Procedures Manual required by NJDOT. The manual itself is prepared as a separate document. The manual contains protocols for FWD testing and analysis for the purpose of project-level rehabilitation design using MEPDG. The developed guidelines clearly define:
• Testing requirements
• Data analysis approach
• Reporting requirements
The protocols are intended to ensure that FWD data is collected and analyzed in a consistent, technically sound, and state-of-practice manner. Appendix A contains FWD Rehabilitation Case Studies to illustrate the methods used to perform rehabilitation analysis using FWD data.