The in-situ evaluation of surface-breaking cracks in asphalt using a wave decomposition method

Abstract

Assessment of the location and extension of cracking in road surfaces is important for determining the potential level of deterioration in the road and in the infrastructure buried beneath it. Damage in a pavement structure is usually initiated in the asphalt layers, making the Rayleigh wave ideally suited to the detection of shallow surface defects. However, the practical application of crack detection methods in asphalt is hampered by the dispersive behaviour of the road pavement. In fact, assessment of crack in road is usually performed assuming constant phase velocity, and its dispersive behaviour is neglected. Moreover, current methodologies for crack evaluation in asphalt do not support in-situ applications. A new digital signal processing technique for the measurement of the amplitude and phase of the direct and reflected Rayleigh waves, scattered from the boundaries of a vertical crack in asphalt, is presented in this paper for the first time. It decomposes the signal into its 2 direct and reflected components. The method uses multiple receivers and hence it finds an approximate solution with a least square optimization. The resonant peak frequencies of the reflection coefficient and the cut-off frequencies of the transmission coefficient are used for assessing the depth of the crack. The study is conducted through numerical simulations alongside experimental investigations and it considers the cases for which the cracking is internal or external to the deployment of sensors. The method proved to be successful for the in-situ assessment of the depth of cracks both numerically and experimentally, since it can cope with the dispersive and heterogeneous nature of asphalt. This work supports a paradigm-shifting approach to in-situ crack evaluation of roads, for which the road is holistically treated as a dispersive medium.

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ORCID for Emiliano Rustighi: orcid.org/0000-0001-9871-7795

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