Resin recovery and the use of computed tomography for quantitative image analysis of railway ballast

Over its life cycle, railway ballast undergoes changes to its fabric structure due to train loading and maintenance (e.g. tamping). Understanding these changes and linking them quantitatively to the loading regime has the potential to inform improved designs for new track and more cost-effective maintenance of the existing network. However, a method for recovering samples of ballast from in service track with the fabric structure preserved for detailed examination is required. This paper describes the development and application of such a method using a polyurethane resin, and demonstrates the ability of powerful X-ray scanners and CT (computed tomography) techniques to construct 3D images of recovered samples up to 300 mm in diameter. It is believed that obtaining preserved samples from in-service railway track and using CT scanning on such large samples have not been done before. To demonstrate the quality and versatility of the CT images illustrative results for CT analysis to measure the coordination number and particle orientation of the field samples obtained are also presented.