Hussein M., Gupta S., Hunt H., Degrande G., Talbot J.

Vibration from railway tunnels has a significant environmental impact on inhabitants of buildings near underground railway lines. The problem is of increasing importance because of the introduction of new underground lines in urban areas, increasing public sensitivity to noise and vibration, and the need to conform to increasingly stringent legislation. There is a great need for railway-design engineers to model vibration from railway tunnels. A model is required to predict absolute levels of vibration from running trains and to assess the performance of vibration countermeasures before being implemented. The model should be accurate and should not require substantial computational resources. This paper presents a new model for calculating vibration from railway tunnels, which combines both accuracy and computational efficiency. The model is based on the assumption that the near field displacement of the tunnel is not influenced by the existence of a free-surface. Displacements at the tunnel-soil interface are calculated using a model of a tunnel wall in a full space, known as the Pipe-in-Pipe model. Green’s functions for a two-and-a-half-dimensional elasto-dynamic full-space are then used to calculate the internal source in a full space that would produce the same displacements at the tunnel-soil interface as calculated by the Pipe-in-Pipe model. The internal source is then used to calculate the far field displacements based on Green’s functions for a two-and-a-half-dimensional half-space. The results and computation time of this model are compared with those of an alternative coupled Finite-Element-Boundary-Element model that accounts for a tunnel wall in a half space.