Influence of Seed Layer Moduli on Backcalculation Procedure and on Overlay Design of Flexible Pavements

Abstract

The seed moduli selected for backcalculation analysis of multilayer flexible pavement can have significant effects on the performance of backcalculation software and, sometimes, the final solutions of the overlay designs. Therefore, this paper aims to analyze the variability of the resilient moduli (MR) obtained by backcalculation programs, taking different seed moduli as input data. To this end, data obtained from non-destructive structural evaluation (falling weight deflectometer [FWD]) were used in three different regions of Brazil. Thereafter, the deflection basin values and the seed moduli were inputted into the two backcalculation methods: linear elastic and finite element. By varying the RM seed of one of the layers by 100%, the percentage differences in the backcalculated moduli were computed within the range of typical resilient modulus (MR) values for paving materials, and close to the upper and lower thresholds of the usual moduli in Brazil. Furthermore, with the data provided by backcalculation software and crack monitoring, these were inputted into the flexible pavement design software (MeDiNa) to also analyze the influence of the seed moduli variability on the pavement overlay design, through the cracked area percentage parameter. Therefore, it was found that the seed moduli have a high influence on the backcalculated moduli, with percentage differences of up to 68.30%, mainly for the base and subbase layers of pavement. Even with the differences obtained in the values of the backcalculated moduli, it was found that the seed moduli did not cause a significant impact on the overlay design in which the percentage difference between the cracking predicted for the surface layer was less than 2.5%.