InSAR monitoring data to assess building response to deep excavations

Abstract

Recently, there has been growing interest to use Interferometric Synthetic Aperture Radar (InSAR) to quantify ground displacements. While InSAR can well determine the area and magnitude of subsidence, very little attention has been paid to explore InSAR measurements to assess the building response adjacent to geotechnical works (e.g., deep excavations, tunnelling). Specifically, few studies have investigated the ability of using InSAR to derive widely accepted building deformation parameters including angular distortion and horizontal strain. On the other hand, geotechnical engineers generally use traditional monitoring data to assess the behaviour of existing structures adjacent to excavations, but often only spatially and temporally limited monitoring data exist to reliably evaluate the governing mechanisms. This contribution follows a case study approach to explore the value of InSAR to quantify the effects of excavation-induced settlements on buildings. Conventional monitoring data of structures adjacent to excavation works for a construction project in Oslo, Norway, are compared to InSAR measurements from satellites with different spatial resolutions and from two different processing methods. Differences between displacements obtained from these different InSAR monitoring datasets and their practical implementation are discussed. Building deformations and respective damage categories are then quantified using a methodology that combines both InSAR and inclinometer measurements. As expected, it was found that high resolution InSAR measurements are more reliable when assessing the building response to excavation works.