Recent research on railway track sub-base behaviour

Abstract

This paper describes some recent and current research on the behaviour of railway track. The main focus is on the deflections of the track as trains pass, and how these may be linked to the stress paths experienced by the ballast and the underlying sub-base. Three questions are addressed: (1) what are the stress paths that soil elements below a railway track are subjected to during train passage?; (2) what is the influence of principal stress rotation on the deformation and failure behaviour of these materials?; and (3) what are the effects of train speed? It is shown that (1) the relevant stress paths may involve principal stress rotation; (2) principal stress rotation may have a significant effect on the behaviour of some soils; and (3) track loading and deflections must be expected to increase with train speed, which may increase load cycling effects. While these conclusions confirm what has been known or suspected for some time, the contribution of the work described in this paper is in beginning to quantify and define boundaries to the significance of these effects.