Effect of Composite Vibration Isolation Walls on Vibrations in the Tunnel Interval Area of Suburban Railways

Abstract Installing vibration isolation walls on both sides of adjacent tunnels in suburban railways can sometimes worsen vibrations between the walls and the source of the vibrations. This study investigates how composite vibration isolation walls affect these vibrations. First, a detailed numerical model of the train-wheel interaction was developed and applied to a 3D track-soil system model, verified for accuracy. The study then explored how single-material vibration walls of different thicknesses amplify vibrations between the walls and the vibration source. It also examined how composite wall material composition and placement affect vibrations in this area. The results showed that using composite vibration walls instead of single-material walls (like EPS) reduced the increase in vibration acceleration and speed at measurement points above the two tunnels. The lowest amplification of peak acceleration at all points (except directly above the tunnel) occurred when C20 concrete was placed closer to the vibration source. For peak velocity, the lowest amplification was found in the central 20-m-wide area between the tunnels when the EPS material was closer to the vibration source. The least amplification of velocity at points directly above the tunnel occurred when C20 concrete was closer to the vibration source. In terms of frequency, choosing the right material ratio for composite vibration walls is essential, as an improper choice can increase the amplification effects.