Structural health monitoring of dams by advanced satellite SAR Interferometry. Investigation of past processes and future monitoring perspectives

Satellite Synthetic Aperture Radar Interferometry (InSAR) techniques and, specifically, Advanced Differential InSAR techniques (A-DInSAR) are becoming, in last years, a powerful tool for the investigation of ground and structure deformations, also thanks to new space missions with last generation sensors able to provide high spatial resolution (about 3x3 m), high displacement accuracy and high sampling rate (up to 4 days) data. This paper describes three successful case histories where such techniques have been applied for the structural health monitoring of dams; specifically, the Three Gorges Dam (China), the Plover Cove Dam (Hong Kong) and the San Liberato Dam (Italy) have been investigated. Both recent high-resolution SAR images and past low- resolution images have been used, depending on specific aims of each case study. In various geographical context, type of structure, kind of satellite sensor used, A-DInSAR technique showed its great potential for reaching specific purposes for every case-study: monitoring the stability of the structure and surroundings areas (Three Gorges Dam), monitoring of the structure response to cyclic stresses investigated by means of recent SAR images (Plover Cove Dam) and analyses of past stability conditions for the health assessment of the dam (San Liberato Dam). The lesson learned by the described case studies is that Advanced Satellite InSAR techniques can be a reliable diagnostic tool in the SHM of dams, especially for long-term investigations or for historical analyses where other monitoring data are lacking.