Ground vibration induced by moving trains on ballasted and rigid tracks using a periodic boundary element formulation

Abstract eng:
The numerical prediction of the groundborne vibration generated by trains has always the requirements of a large amount of computational time, since the models should usually be extended far away from the track and, in many cases, an appropriate absorbing boundary should be placed at the end of the discretization to ensure the waves to propagate towards the infinite. These problems can be better handled using the Boundary Element Method (BEM) method, which naturally avoids the interior domain discretizacion, accounting appropriately for the unbounded characteristics of the media. However, many of these BEM models should still be extended to long distances over the surface of the ground, becoming sometimes very time-consuming. When considering that the track and soil have constant properties and geometry along track direction, the problem can be significantly reduced by taken into account the periodicity of the displacement and tractions fields. This property allows considering a very much reduced discretization of the media. A new procedure is proposed in this paper, using the symmetry and asymmetry decomposition of the model and working in the frequency domain. The goal of the proposed method is to provide an easy implementation in standard codes since it reproduces the usual workflow in them, not requiring any especial formulation. The periodic domain is represented in the model by a discrete module of the mesh. In the original model, this module is repeated towards the infinite, forward and backward. When the separation planes between the reference module and the two consecutive modules are defined as symmetry planes, the discretization of the modules apart from the reference module can be avoided. A significant reduction of mesh size and time calculation is obtained with the proposed method. The procedure is applied to obtain the train-induced vibration in the soil for different track and soil configurations. The symmetry decomposition is applied as well to the FEM part of the model. The train induced vibration for ballasted and rigid track cases is obtained using a very simple model. The reduced mesh obtained considering periodicity allows representing the track area in much more details than usual models or considering soil no homogeneities.

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