Esposito, Ilaria (2026) Static and dynamic effects of deep excavations on the surroundings: two case studies in Napoli. [Tesi di dottorato]

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Abstract

The thesis has the aim of providing an additional contribution to the state of the art by filling some gaps found in the literature referring to the understanding and quantification of deep excavations effects on buildings and nearby facilities, both in static and dynamic conditions. Two case studies of deep open-pit excavations carried out in the center of Napoli are used as a starting point. These are Chiaia and San Pasquale stations on Line 6 of the Napoli metro, whose effects on the surrounding environment have been investigated both statically (during construction, by conducting a very detailed back-analysis based on monitoring data) and seismically (hypothetical scenario of seismic loads) using three-dimensional modeling of the case studies on finite element software, in which the construction phases, the interaction between the support structures and the ground, and the non-linear behavior of the soil are accurately reproduced. In addition to an introductory chapter (Chapter 1), the thesis is structured as follows: Chapter 2 presents the state of the art in underground works, with particular attention to large-scale excavation projects. After an introduction on construction technologies and Italian and European regulations, the chapter is divided into two parts: one concerning the statics of excavations and the methods, both recent and less recent, for calculating the stresses resulting from interaction with the ground, the induced displacements, and for assessing damage to buildings; the second part is dedicated to soil-structure interaction under seismic loads: this includes a section on structure-soil-structure interaction, with particular attention to the interaction of underground structures with the surrounding environment and therefore also with above-ground structures, and vice versa. Chapter 3 is dedicated to the case study of Chiaia station. An introduction describing the case study and the monitoring results, is followed by a static back-analysis of the construction process, which investigates and highlights the role of various modeling details, including the assumptions necessary for a simplified but rational modeling of the buildings of greatest interest. Finally, the construction of the numerical model and the results of the coupled dynamic analyses are presented with particular reference to the effects induced on the buildings in terms of displacements and peak ground accelerations. Chapter 4: San Pasquale station is the case study covered in this chapter, which follows the same structure of the previous one. Compared to the Chapter 3, however, greater attention is paid to the structural modeling of the buildings affected by the most significant subsidence and, thanks to the characteristics of the case study in question, it has been possible to parameterize the analyses carried out under seismic excitation to a greater extent, placing emphasis on the spatial distribution of the quantities of interest. Chapter 5 reports on the simulation using FEM analysis, and subsequent comparison, of centrifuge experiments conducted to characterize the seismic behavior of a rectangular tunnel in dry sand. The chapter aims to characterize the capacity of the tools used in numerical analysis to reproduce experimental data. Chapter 6: the results presented in the thesis are summarized in this concluding chapter which, in addition to referring to individual case studies, contains some general considerations validated in the thesis by comparison with the existing literature, mainly referred to tunnels, which is almost the only reference point, since open deep excavations are scarcely investigated.

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