The study of the interlock of ballast in triaxial geogrids

Rail transport is the most efficient way of transport from an energetic and environmental point of view. The integration of geosynthetics in the rehabilitation solutions has grown substantially in the last decade, such as the application of different geogrids for reinforcement and/or stabilization of ballast layer. It appears to be consensual that the effectiveness of the geogrid depends on the degree of interlock between the geogrid and the granular material. The main purpose of this study is to analyse the relation between the geogrid aperture size and the ballast size that maximizes the interlock. The influence of the geogrid location in the ballast layer and the ballast grading are also addressed. The results suggested that, in order to obtain a higher interlock percentage, a selected ballast layer, with a reduced maximum dimension, should be used in contact with the geogrid and the geogrid should be placed in the ballast layer, above the interface ballast/substructure. The results suggested that the relation between the geogrid aperture size and the maximum dimension of the aggregate should be around 1.22 in order to improve the interlock.