Geotechnical aspects of underground railway construction in the urban environment: the examples of Rome and Naples

Abstract This paper presents some of the geotechnical aspects of underground railway construction in the urban environment, drawing from recent experience gathered during the design of the new Line C of Rome Underground and the construction of Line 1 of Naples Underground. For Rome Underground, the paper summarizes the main results of a study of the interaction between tunnel construction and a monumental structure at the surface. The assessment of the potential damage induced by tunnelling was approached following stages of increasing complexity, from simple and well-established semi-empirical methods to 2D and 3D numerical soil–structure interaction analyses. A significant joint effort from archaeologists and geotechnical and structural engineers was required to define reliable models of the monument and of the subsoil ground conditions. For Naples Underground, this paper describes the construction techniques that were implemented to build the open excavations required to accommodate the stations, including artificial ground freezing, and illustrates some of the analyses that were carried out to interpret the observations of the ground behaviour and of the behaviour of the structures during construction.