ABSTRACT
In Italy, the modernization of infrastructure in populated areas is leading to a very intensive occupation of the underground space with tunnels and other horizontal lifelines. The increased number and variety of intersections with surface and deep infrastructures and the demanding performance required by modern standards (e.g. high-speed railways), place particular relevance to the prediction of the effects (stresses, movements, distortion) and, more generally, to the vulnerability and serviceability of the involved systems. Given the complexity of the mechanism determined by a concurrence of factors like the geometric and mechanical characteristics of the involved structures, the mechanical response of the subsoil and the construction techniques, simplified solutions are often adopted. Technical Literature offers many studies that provide a geometric description of the free field ground subsidence basins determined by tunnelling and to its correlation with the damage of buildings. On the other hand, there are few studies correlating the tunnel induced subsidence to the effects on existing railway infrastructures.
Aim of this paper is to analyse the effects of mechanized tunnel construction on the track twist of railways running at the ground level and provide some rule on the limits established for design. A parametric study has thus been carried out, inspired by a real example, varying the tunnel cover and the angle between the future tunnel and the existing infrastructure. For the sake of generality, the study covers sand and clay soils and results are summarised with graphs.
