Time-frequency analysis of air-coupled GPR data for identification of delamination between pavement layers

Abstract

Identification of delamination in pavement layers using ground penetrating radar (GPR) is still challenging due to its limited range resolution. This paper investigates the characteristics of the composite reflection from the air-filled delamination between pavement layers by time-frequency analysis. We firstly simulated GPR data from an asphalt pavement model with an embedded air gap of different thicknesses by the Green’s function method. Then we conducted a laboratory experiment on a delaminated asphalt pavement model. Both the numerical and laboratory experiment results demonstrate that both the peak instantaneous frequency and its amplitude are sensitive to the variation of the air gap thickness. When the thickness of the air gap is smaller than a quarter of the dominant wavelength, the peak instantaneous frequency of the composite reflection is higher than that of the normal interface reflection. We conclude that we can identify the delamination from the overall rise in the peak instantaneous frequency.