MODELLING OF VIBRATIONS INDUCED BY TRAFFIC IN TUNNELS : FROM THE SOURCE TO THE RECEIVER

The simulation and study of problems related with vibrations induced by railway traffic in tunnels is a difficult and complex task. Actually, the complexity of the problem can be attributed to the vast field of analysis, which comprises not only the generation of vibrations inside the tunnel as well as its propagation through the ground and its interaction with existing buildings in surroundings. In the present paper a numerical procedure is presented in order to allow an efficient simulation of the vibrations induced by traffic from the source to the receiver (building). The numerical model is divided into three distinct parts, comprising the simulation of rolling stock, the simulation of the tunnel-ground system and the simulation of the building. The solution is obtained by a compliance formulation between the three subsystems, developed in the frequency-(wavenumber) domain. Regarding the simulation of the tunnel-ground system, which deals with unbounded domain problem, an efficient solution is developed using a 2.5D technique based on the finite elements method, and adopting perfect matched layers (PML’s) for the treatment of the boundaries due to the truncation of the finite elements mesh. The numerical model is used to study the vibrations induced inside of a simple building close to a shallow railway tunnel. From the study performed, it was possible to conclude that the dynamic characteristics of the building, namely the natural frequencies of resonance of the slabs, play an important role in the problem. Patrícia Lopes, Pedro Alves Costa, Miguel Ferraz et al. 2

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