ABSTRACT
This was the case in a project to improve the rail access to a new mining development in the Caribbean which is expected to carry freight traffic of 11 million tonnes per annum at a line speed of 25 mph.This project involved designing trackbed layers for major upgrades to existing rail lines and the installation of new railway infrastructure. Extensive and detailed site and ground investigations where carried out as a preliminary phase of design (Brough et al. 2006) to determine the extent of subgrade variation. Additional laboratory tests were carried out to determine the mechanical behaviour of locally derived stone proposed as ballast for the construction as this differed considerably from the materials specified in the main design standards. The differences in subgrade and loading conditions envisioned in this design were significantly different from those encountered when using most standard design methods. For this reason it was decided to use a number of design methodologies to determine the depth of construction required to protect the subgrade and then to assess which method was
most appropriate for each section of line. The methods used in the analysis are the most commonly applied national standards and a linear elastic model used by Scott Wilson for designing highway pavements, suitably modified to allow for rail wheel loading.
