A Numerical Investigation of Railway Ground Vibration Mitigation Using a Trench in a Layered Soil

Ground vibration from railway lines at grade often has its highest amplitudes at frequencies around or even below 10 Hz. A ground vibration ‘barrier’ (i.e. an open or in-filled trench) would be an attractive means of mitigation of vibration since it would not interfere with the engineering or operation of the track. However, before detailed research, a preliminary theoretical study was conducted to test the idea since simple considerations suggest that barriers might have to be unfeasibly deep to be effective. However, the layered ground structure is known to be important in determining the spectrum of transmitted vibration and recent practical investigations suggest that trenches of reasonable depth may be effective. As a prelude to more detailed investigations, an investigation has been carried out using a two-dimensional coupled finite element (FE) and boundary element (BE) model. The results indicate that, in the peak frequency range of vibration transmission, for a typical alluvial valley site, reductions of 4 dB at 10 Hz and 8 dB at 14 Hz might be achieved with a 5 m deep trench.