A Non-Invasive and Multi-Scale Approach to Detect Subsidence in Pavements: InSAR, FWD and GPR

This paper presents a non-invasive and multi-scale approach to detect subsidence in a national road through the combination of complementary techniques, InSAR (Interferometric Synthetic Aperture Radar), FWD (Falling Weight Deflectometer) and GPR (Ground-Penetrating Radar). For the InSAR, the PSI (Persistent Scatter Interferometry) method was selected using Sentinel-1 images. The FWD measurements were collected with 100 m spacing. The GPR survey was conducted with air-coupled antennas of 1.0 and 1.8 GHz central frequencies. The approach herein presented has demonstrated to be an efficient tool to detect subsidence: at network level, the InSAR allowed to detect differential settlements in transition zones and subsidence due to soil consolidation in high embankments; whereas, at project level, the GPR enabled to detect changes in the pavement structure, while the FWD measurements were used to differentiate weaker/stiffer pavement sections. This approach opens new possibilities for diagnostic procedures to optimize the measurement location of costly and time-consuming GPR and FWD tests.