3D AND 2D NUMERICAL MODELS OF MECHANISED EXCAVATION OF OVERLAPPED TUNNELS IN URBAN AREA: SENSITIVITY ANALYSIS FOR THE EVALUATION OF INDUCED SETTLEMENTS AND BUILDING DAMAGE VARYING THE EXCAVATION SEQUENCE

In the world the increasing need of the improvement of the transportation infrastructures led to the construction of twin tunnels at shallow depths. For this reason, the aim of this thesis is to analyse the interaction between two overlapped tunnels changing the construction process. To do that, the project of the metro M5 of Bucharest is taken as reference for the developed 3D and 2D numerical models. The FEM analysis is performed using the software MIDAS FEA NX and PLAXIS 2D. In particular, the ground surface settlement induced by the tunnelling excavation is the main issue of the twin tunnel construction, hence some theories able to describe this problem are highlighted. After that a sensitivity analysis to understand the building induced damages, based on the results of the 2D model, is conducted with the final purpose to build a risk matrix for a building placed in the settlement trough caused by the excavation.