Abstract
The aim of this paper is to describe how ground-based radar interferometry can provide displacement measurements of earth dam surfaces and of vibration frequencies of its main concrete infrastructures. In many cases, dams were built many decades ago and, at that time, were not equipped with in situ sensors embedded in the structure when they were built. Earth dams have scattering properties similar to landslides for which the Ground-Based Synthetic Aperture Radar (GBSAR) technique has been so far extensively applied to study ground displacements. In this work, SAR and Real Aperture Radar (RAR) configurations are used for the measurement of earth dam surface displacements and vibration frequencies of concrete structures, respectively. A methodology for the acquisition of SAR data and the rendering of results is described. The geometrical correction factor, needed to transform the Line-of-Sight (LoS) displacement measurements of GBSAR into an estimate of the horizontal displacement vector of the dam surface, is derived. Furthermore, a methodology for the acquisition of RAR data and the representation of displacement temporal profiles and vibration frequency spectra of dam concrete structures is presented. For this study a Ku-band ground-based radar, equipped with horn antennas having different radiation patterns, has been used. Four case studies, using different radar acquisition strategies specifically developed for the monitoring of earth dams, are examined. The results of this work show the information that a Ku-band ground-based radar can provide to structural engineers for a non-destructive seismic assessment of earth dams.
Highlights
Synthetic Aperture Radar (SAR) interferometry is a mature technique for the measurement of displacements, using both spaceborne, airborne and ground-based SAR sensors
As the goal of this paper is to demonstrate that a ground-based radar can provide useful information to the sophisticated analysis tools needed for earthquake analysis, different acquisition strategies have been adopted to measure the dam displacements with simultaneous downstream and upstream radar measurements and specific data acquisition schemes for estimating different components of the displacement vector
We summarize the results obtained within the AIM-DAMS project for the monitoring of earth-filled dams by using Ground-Based Synthetic Aperture Radar (GBSAR) and RAR interferometry
Summary
Synthetic Aperture Radar (SAR) interferometry is a mature technique for the measurement of displacements, using both spaceborne, airborne and ground-based SAR sensors It has been applied to monitor geological phenomena such as landslides [4,5,6,7], subsidence [8,9], volcanic activity [10] and infrastructure [11,12]. In this work we focus on the monitoring of earth dams, an example of infrastructure of extreme importance for agricultural practices and water resource management. There are few papers covering this specific application where spaceborne SAR data have been used to measure earth dam displacements [13,14,15,16]. In [13], the earth dam was still not in operation
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