A Study of the FWD Deflection Characteristics of Composite and Sandwich Pavements

Abstract

A study was carried out on the falling weight deflectometer (FWD) deflection data obtained from road pavements in the South Coast region of Queensland. The pavement structures consist of the conventional asphalt granular pavement, composite and “sandwich” pavements construction. The FWD deflection characteristics of the three pavement structures were studied using a simplified deflection model (SDM). The mathematical expression for the SD model is.The exponential curve was found to have the desired characteristics which match the FWD deflection bowls. In the equation, Y is the FWD deflection in microns and X is the radial distance in millimeters. The coefficients K1 and K2 of the model describe the structural characteristics of the pavements. The results indicate that the coefficient K1 and K2 are unique for the three pavement types with relatively thin asphalt and sealed coat layers. The study suggests that the coefficient K1 is closely related to strength of the subgrade and K2 is dictated by the deflection ratio, DR, of the FWD deflection curve. The deflection data generated with SDM were compared with the deflection results obtained from ELSYM5. The study showed that SDM models the FWD deflection more accurately for granular pavements with thin surfacing layers.