FE Modelling as a Design Tool for Mitigation Measures for Railway Vibrations

In Scandinavia, soft clay ground conditions often lead to complaints about annoying vibration in dwellings along railway lines. Since the effectiveness of vibration mitigation measures is highly dependent on the ground conditions, advanced methods such as FE-modelling usually need to be used when countermeasures are evaluated. However, for these methods to be suited for use as design tools, it is essential that the models are relatively easy to set up, have reasonably short computational times and do not require time-consuming post processing before the results can be obtained. It is therefore desirable to use 2D models to the greatest possible extent. In this paper we investigate the feasibility of using 2D models when calculating the effect of mitigation measures. We consider both low frequency vibrations from a railway line on soft ground with a screen as the mitigation measure, and more high frequency vibrations causing structure borne noise from a tunnel in clay with soft under-ballast mats as the mitigation measure. The results show that 2D models are suited as design tools as long as root mean square values of vibration velocity are considered, and the results are primarily used to compare different mitigation measures. Since geometrical attenuation is not correctly captured in 2D models, they should not be used to calculate absolute vibration values.