Simplified Closed-Form Procedure for Network-Level Determination of Pavement Layer Moduli from Falling Weight Deflectometer Data

Abstract

Accurate estimation of the layer moduli for an existing pavement system is a key element for making an effective decision on pavement rehabilitation. Backcalculation is one of the most widely used processes for analyzing falling weight deflectometer (FWD) data to estimate pavement layer moduli. Though many software packages are available for this process, the results have been found to be very sensitive to program features and operator skills and level of experience. This paper aims to develop a simplified procedure to backcalculate pavement layer moduli for three-layered sections (surface, base, and subgrade) using a closed-form procedure. Seven three-layered Long-Term Pavement Performance (LTPP) sections with 723 FWD test points were used to develop and validate the proposed procedure. The structural number of the existing pavement (${\mathrm{SN}}_{\mathrm{eff}}$ ) at the time of the FWD application was used in the analysis. The developed procedure yielded accurate and reasonable modulus values for the asphalt concrete ($E_{\mathrm{AC}}$ ) with a coefficient of determination ($R^2$ ) of 0.891, while it yielded reasonable base modulus ($E_B$ ) values with $R^2$ of 0.769 when compared with the LTPP backcalculated modulus values. The developed closed-form procedure is recommended for the estimation of pavement layer moduli at the network level.