Double wall barriers for the reduction of ground vibration transmission

Stiff wall barriers can be effective in reducing the transmission of environmental ground vibration. Up to now, single wall barriers have mostly been studied. In building acoustics, however, double walls are used in order to realize a high level of sound insulation. In this paper, the potential of using double walls in reducing ground vibration transmission is investigated by means of numerical simulations. Two cases are studied: jet-grout walls and concrete walls in a homogeneous soil with elastic properties representative of a sandy soil. For both cases, the three-dimensional free field response due to a point load is computed using a 2.5D finite element methodology. Subsequently, the free field response is computed for a simplified train load. Double jet-grout wall barriers are found to be slightly more effective than single wall barriers, in particular when the thickness of the walls and the intermediate soil matches a quarter Rayleigh wavelength. The largest increase in vibration reduction is found for the area closest to the vibration source, where the vibration levels have the highest values. The performance of concrete wall barriers, however, is mainly determined by the stiffness of the walls, and almost no difference in performance is found for single and double walls.