3D And 2D Numerical Models Of Mechanised Excavation Of Overlapped Tunnels In Urban Area: Sensitivity Analysis Of The Stresses And The Strains In the segmental tunnel Lining 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 model. The FEM analysis are performed using the software MIDAS FEA NX and PLAXIS 2D. As first, the segmental tunnel lining is described considering all the parts and materials which compose it, in order to understand the answer of the model to the change of the excavation sequence. Moreover, the theory behind the structural behavior of the segmental tunnel lining of both the tunnels, is highlighted in order to evaluate if the induced forces and moments, extracted from the numerical model, can be compared with the resistances of each ring. Finally, it is also possible to assess which is the preferable solution for the excavation sequence, focused mainly on the tunnels system structure and on its operation and durability during the service life of the tunnel.