Imaging Multi-Age Construction Settlement Behaviour by Advanced SAR Interferometry

Abstract

This paper focuses on the application of Advanced Satellite Synthetic Aperture Radar Interferometry (A-DInSAR) to subsidence-related issues, with particular reference to ground settlements due to external loads. Beyond the stratigraphic setting and the geotechnical properties of the subsoil, other relevant boundary conditions strongly influence the reliability of remotely sensed data for quantitative analyses and risk mitigation purposes. Because most of the Persistent Scatterer Interferometry (PSI) measurement points (Persistent Scatterers, PSs) lie on structures and infrastructures, the foundation type and the age of a construction are key factors for a proper interpretation of the time series of ground displacements. To exemplify a methodological approach to evaluate these issues, this paper refers to an analysis carried out in the coastal/deltaic plain west of Rome (Rome and Fiumicino municipalities) affected by subsidence and related damages to structures. This region is characterized by a complex geological setting (alternation of recent deposits with low and high compressibilities) and has been subjected to different urbanisation phases starting in the late 1800s, with a strong acceleration in the last few decades. The results of A-DInSAR analyses conducted from 1992 to 2015 have been interpreted in light of high-resolution geological/geotechnical models, the age of the construction, and the types of foundations of the buildings on which the PSs are located. Collection, interpretation, and processing of geo-thematic data were fundamental to obtain high-resolution models; change detection analyses of the land cover allowed us to classify structures/infrastructures in terms of the construction period. Additional information was collected to define the types of foundations, i.e., shallow versus deep foundations. As a result, we found that only by filtering and partitioning the A-DInSAR datasets on the basis of the above-mentioned boundary conditions can the related time series be considered a proxy of the consolidation process governing the subsidence related to external loads as confirmed by a comparison with results from a physically based back analysis based on Terzaghi’s theory. Therefore, if properly managed, the A-DInSAR data represents a powerful tool for capturing the evolutionary stage of the process for a single building and has potential for forecasting the behaviour of the terrain–foundation–structure combination.

Measuring Urban Subsidence in the Rome Metropolitan Area (Italy) with Sentinel-1 SNAP-StaMPS Persistent Scatterer Interferometry

“…The southwest of the study area is dominated by the Tiber River delta and coastal plain. Both are comprised of alluvial sediments with a flat morphology [12]. The northeast of the study area includes the beginning of the Apennines mountain chain, comprising mainly sedimentary limestone and dolomite rocks [13].…”

“…Subsidence of buildings on the alluvial sediments along the Tiber River in Rome has been measured using PSI, Small Baseline Subsets (SBAS), Interferometric Point Target Analysis (IPTA) and 4D SAR imaging techniques in many studies, e.g., by [11,[15][16][17] and others, using ERS-1, 2 and ENVISAT ASAR data. The main cause of subsidence in this case is the weight of relatively recent construction on the unconsolidated alluvial material, especially in areas such as Grotta Perfetta, in the southwestern outskirts of the city [11][12][13][14][15][16].…”

“…In this study we employ such open tools to analyze the urban deformation of the Rome metropolitan area for the first time using Sentinel-1 data, and combined ascending and descending orbits to depict the vertical urban deformation with special attention to different areas. Ground deformation analyses of Rome have already been undertaken in the past [11,12], but these have not been updated recently, and have not included Sentinel-1 SAR observations. Here we intend to update existing knowledge with contemporary information regarding ground deformation in the Rome metropolitan area using open data and tools.…”

Pre-Collapse Space Geodetic Observations of Critical Infrastructure: The Morandi Bridge, Genoa, Italy

“…There is a wealth of scientific literature demonstrating the benefits of InSAR to monitor a wide spectrum of urban processes, such as subsidence [2][3][4][5], foundation settlement [1,6,7], deformation of new buildings [8], surface effects due to tunneling [9][10][11], ground motions associated to faults and local tectonics [12][13][14]. The implementation on real case studies proves the increasing use of these techniques on a routine basis and how they can influence the management of infrastructure assets and preservation of the built environment [1,15,16].…”

A Model for Complex Subsidence Causality Interpretation Based on PS-InSAR Cross-Heading Orbits Analysis

“…The interaction between causal factors is clear in many cases [13]. Nevertheless, the interaction between different factors is normally treated descriptively in large areas as in Seleem et al [8], or mathematically in very small areas such as at building scale [13], and relatively few studies integrate spatially two or more causes when interpreting a pattern of subsidence in a city scale or larger areas of interest [14]. Hence, in this study, we propose a new model to interpret and map the complex subsidence causality (CSC) based on the number of spatially dependent factors that contribute to subsidence in a given area of interest.…”