Evaluating the effect of vibration isolation mats on train-induced ground vibrations

In the present paper, the effectiveness of a vibration isolation mat for a railway slab track system is studied using a finite element model of the railway track. The finite elements are formulated in a moving frame of reference following the moving load at a particular speed. The rails are modeled using Bernoulli beams, whereas the track slab and an underlying supporting plate are modeled using Kirchhoff plate elements. The vibration isolation mat is modeled as a continuous visco-elastic layer between the track slab and the supporting plate. The response of the underlying soil is represented through a dynamic stiffness matrix, obtained via the Green’s function for a horizontally layered visco-elastic strata in a moving frame of reference in the frequency– wavenumber domain. The model accounts for the quasi-static excitation caused by the static axle loads of a vehicle, as well as the dynamic excitation caused by the vehicle running over an uneven rail. The free-field response and the insertion loss obtained with the vibration isolation mat is first evaluated for a harmonic load moving along the track. Band-averaged vibration levels and the insertion loss for a fixed point next to the track are then calculated for a train cart, represented by a 10 degree-of-freedom multi-body system, running at different speeds.