Evaluation of railway trackbed and formation: a case study

To determine the causes of poor track geometry, a trackbed investigation should comprise a full assessment of ballast, sub-ballast and formation condition. If information about any of these layers is omitted, the true cause of poor formation sites cannot be ascertained satisfactorily and consequently appropriate ground improvement schemes may not be implemented. This has been observed in the UK rail network with examples of a lack of detailed site investigation and subsequent expensive remedial work being carried out without eliminating the initial cause of the problem. This paper summarises the trackbed investigation performed at a site requiring high maintenance, suspected as being caused by poor formation. The paper concludes with an analysis of ground conditions and possible choice of remedial schemes.