Gb-SAR interferometry displacement measurements during dewatering in construction works. Case of La Sagrera railway station in Barcelona, Spain

Construction processes require monitoring to ensure safety and to control the new and existing structures. Traditional monitoring is based on land surveys and geotechnical instruments and only allows for point-like measurements. Ground-based synthetic aperture radar (GB-SAR) is a remote sensing radar installed in the ground that offers the possibility of acquiring measurements in 2D covering areas of up to a few square kilometers in a single acquisition. Because the GB-SAR technology measures phase shifts along the Line-of-Sight, it only allows for measurements in the longitudinal direction. Moreover, this technology requires coherence between subsequent acquisitions. These restrictions can be a limitation to the usage of GB-SAR for monitoring a construction process because in this context, the movements of soil and existing structures occur in any direction and at a very fast pace. This paper aims to test the GB-SAR suitability to measure movements during construction. To do so, an experiment was performed in the future railway station of La Sagrera, Barcelona (Spain), in which GB-SAR was used to accurately quantify wall displacements induced by dewatering and proved to be helpful to understand structural deformations and to identify vulnerable areas. The results were compared to traditional monitoring data and numerical models to confirm the reliability of the GB-SAR measurements.