Synergistic monitoring of transport infrastructures by multi-temporal InSAR and GPR technologies: a case study in Salerno, Italy

Advances in data processing and the availability of large datasets from very high-resolution (VHR) SAR satellite missions are promoting the use of multi-temporal InSAR techniques for the near-real-time assessment and the health monitoring of bridges and transport infrastructures. On the other hand, the Ground-Penetrating Radar (GPR) is a Non-destructive technology widely applied to monitor the internal state of infrastructure asset by rapid electromagnetic inspections. This research aims to investigate the viability of a novel Non-Destructive Health-Monitoring Approach (ND-HMA) based on the synergistic use of satellite remote sensing and GPR techniques for structural assessment of bridges and the prevention of damages induced by structural subsidence. The analyses were developed to identify and detect structural displacements of the Olivieri Bridge, located in Salerno, Italy. To this purpose, commercial VHR COSMO-SkyMed (CSK) products, provided by the Italian Space Agency (ASI), were acquired and processed by persistent scatterers (PS) InSAR technique. The historical time-series of deformations of the scatterers, found in correspondence of critical structural elements of the structure (i.e., bridge piers and arcs), were analyzed. Furthermore, in-situ GPR inspection analysis were carried out by using multi-frequency GPR systems equipped with both air-launched and ground-coupled antennas with central frequency ranging between 200 MHz and 1000 MHz. The implementation of the integrated approach provides a technologically enhanced and reliable mechanism for the provision of "early warning" information to be more rapidly processed and conclusively actioned by asset owners and management agencies. In particular, a novel data interpretation approach is proposed based on the selection of several PS data-points with coherent deformation trends on the bridge and the analysis of GPR outputs. The outcomes of this study demonstrate that multi-temporal InSAR remote sensing techniques can be applied to complement non-destructive ground-based analyses (e.g., ground-penetrating radars), thereby paving the way for integrated approaches in the smart monitoring of infrastructure assets.