Keywords: railway vibration, high speed rail, vibration mitigation, wave barriers, trenches.

This paper investigates the effect of construction dimensions on the ability of wave barriers in reducing ground vibration levels from high speed rail lines. Wave barriers are used to shield structures located near railway lines from elevated vibration levels, but their construction costs are typically high. This is due to large excavation costs and subsequently large infill material costs. Therefore a combination of experimental and numerical tests are used to show that wave barrier dimension optimization can be used to significantly reduce construction costs while maintaining high isolation performance.

Firstly, experimental investigations are undertaken on the Paris-Brussels high speed line for the purpose of sampling vibration levels at distances up to 100m perpendicular to the track. These vibrations are recorded using a combination of three component and one component geophones placed at distances up to 100m from the track. Multi-channel analysis of surface waves tests are also performed to determine ground profile information. The soil parameters are verified using refraction tests and material damping, in the form of Rayleigh damping, and calculated using a curve fitting approach.

The development of a dynamic, three dimensional, explicit integration, time finite element railway model is then detailed. It is composed of three components: the train, track and soil. The soil is modelled as a linear elastic unbounded domain which is truncated using infinite elements. The track is modelled in accordance with that found on high speed lines throughout Europe. The locomotive is modelled using a multi-body approach, with lumped masses used to describe the individual vehicle components. It is coupled to the rail using a non-linear Hertzian spring. This model is used to perform simulations replicating the soil, track and train configuration uncovered at the experimental test site. The simulated vibration levels are then compared to the experimental data and it is shown that the model is capable of predicting vibration response due to train passage with high accuracy.

The model is then extended to investigate the effectiveness of trench wave barriers in mitigating ground borne vibrations from railway lines. The wave barriers are assumed to be constructed from a low density material such as polyurethane. A wide range of simulations are performed to investigate the effect of barrier width, depth, length and distance from the track on vibrations. All trench dimensions are normalised with respect to the dominant Rayleigh wavelength propagating within the soil and a standardised amplitude reduction approach is used to assess wave barrier performance. It is found that depth and length have a strong influence on the mitigation of vibration levels but the effect of trench width and distance from the track is negligible.

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