De Luca, Manuel (2025) A multi-scale investigation of ground movements around deep excavations through satellite monitoring, physical testing and numerical analysis. [Tesi di dottorato]

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Abstract

This research develops a multi-scale investigation to improve the prediction and monitoring of ground settlements caused by complex deep excavations in urban environments. The framework integrates numerical analysis (in a three-dimensional environment), physical tests and satellite-based monitoring, reflecting the inherently multifaceted nature of deep excavations and addressing their complexity through complementary perspectives. (1) Differential Interferometric Synthetic Aperture Radar (DInSAR) is applied to monitor ground deformation around excavation sites, improving spatial and temporal coverage beyond conventional surveys. The comparison with topographical monitoring is conducted systematically, using multiple scales of representation to assess and interpret any mismatches between the two datasets. Case studies in Napoli are used to assess the reliability of the technique for capturing localized excavation-induced displacements across different radar frequencies (C-Band vs. X-Band, different scatterer densities and satellite acquisition geometries). A novel correction methodology is then introduced to remove large-scale ground movement components from the satellite data, isolating localized effects of the excavations. (2) Physical model tests (centrifuge experiments) are performed to produce prototype-scale excavation settlement data, simulating various excavation conditions in sandy soils. Following the numerical back-analysis of centrifuge tests, parametric studies are conducted to assess the influence of key factors characterizing the settlement field around the excavation shafts. Furthermore, centrifuge-derived numerical models are employed to validate and refine correlations deriving from the representation of the subsidence effects by means of a three-dimensional subsidence analytical function, proposed in recent literature (Russo and Nicotera, 2022). (3) Finally, three-dimensional finite element (FEM) analysis is employed to simulate a complex real excavation scenario (the Arco Mirelli station in Napoli) to conduct an evaluation of its effectiveness in detecting displacements around the excavation shaft. The outcomes of the analysis are discussed with reference to the correspondence between predicted and observed displacements, by analyzing the potential of the back-analysis process in identifying the main factors governing the response to this type of excavation, and with the ultimate objective of improving the design approach for similar cases.

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