Finite element analysis of the excavation of the new Garibaldi station of Napoli underground

This paper describes the excavation for the new Garibaldi Station of Napoli Underground, completed in October 2004. The 44 x 20 m2 rectangular excavation, with a maximum depth of 45 m bgl., was protected by 1 m thick concrete diaphragm walls excavated using a hydromill, in 2.5 m wide panels. The excavation was carried out top down, support being provided by the floors of the station and by several levels of anchors. The paper describes a finite element analysis of the construction of the structure and a comparison of the numerical predictions with the observed behaviour. Before modelling the main sequence of excavation and propping and the changes of pore water pressures due to the excavation works, the sequence of panel excavation under bentonite slurry and concreting was examined. A significant effect of modelling wall installation versus wished in place wall analyses was found in terms of displacements of the wall and ground surface at the back of the wall, prop forces and bending moments within the wall. The available measurements were used both to assess the numerical predictions, in terms of diaphragm displacements, and to guide in the way in which some support elements, e.g. anchors, should be treated in the analyses. © 2006 Taylor & Francis Group