A methodology based on 2.5D FEM-BEM for the evaluation of the vibration energy flow radiated by underground railway infrastructures

Abstract

In this paper, a comprehensive numerical approach for modelling track/tunnel/soil systems in the context of ground-borne railway-induced vibration problems considering a full-space model of the soil is proposed. All the approach is formulated in the wavenumber-frequency domain and it consists of a coupled finite element–boundary element model of the tunnel/soil system, a semi-analytical model of the track, a multibody model for the vehicle and a model for the vibration propagation in the soil based on semi-analytical solutions of a cylindrical cavity in a full-space. This comprehensive approach has been developed with the aim of computing the vibration energy flow radiated upwards by underground railway tunnels. An axisymmetric formulation to deal with circular underground railway tunnels is included in the approach in order to improve the computational speed of the methodology. This formulation can also be used for other types of railway tunnels if a circular boundary of the boundary element mesh is considered. Since this methodology uses finite elements to model the tunnel structure, its modelling detail is higher than the previously developed methodologies dedicated to compute the vibration energy flow radiated by underground railway infrastructures, since they are based on semi-analytical modelling of the tunnel structure. The present methodology has been specifically designed to be used in general assessment studies about ground-borne underground railway-induced vibrations where decisions on the type of track and/or the application of mitigation measures at the source, as soft rail-pads, under-ballast or under-slab mats, have to be made. Moreover, this methodology can be used for the study of the vibration radiation patterns of railway tunnels.