Network-Level Falling Weight Deflectometer Testing

Abstract

A project was initiated to collect network-level falling weight deflectometer (FWD) data along Virginia's Interstate system. The FWD data collection aims to build a comprehensive database of deflection data and associated structural analysis to be used for future implementation of the Mechanistic–Empirical Pavement Design Guide. Virginia's current network-level evaluation protocol requires that pavements be tested every tenth of a mile at four drop levels, with three deflection basins (repetitions) collected at each drop level. To test the more than 2,000 lane miles of Interstate system, it was necessary to determine if the number of test points per mile and the number of load levels used could be reduced to increase the testing production rate and reduce the high cost of testing and traffic control. FWD testing was initiated on the entire length of I-77 and on portions of I-64 and I-81 by using the current testing protocol with only two deflection basins collected at each drop level. A comprehensive statistical analysis was performed on subgrade moduli, effective structural number, and layer moduli calculated by using the AASHTO and the ELMOD methods, respectively. The results of this study document that network-level testing at 10 points per mile can be reduced to three points per mile, and the four FWD drop levels can be reduced to only one drop level, with two deflection basins collected at this load level, without statistically compromising the quality of the data collected. However, the recommendation was made to collect data at multiple load levels for future in situ characterization of material stress sensitivity.