ABSTRACT
ABSTRACT: This paper describes experiences in the use of biaxial geogrids in rail applications. Since their first use more than 25 years ago, geogrids have been used for ballast/ sub-ballast reinforcement on many occasions on main line track projects, industrial rail spurs and the development of intermodal yards. Incorporated within unbound aggregate layers, geogrids interact with the surrounding aggregate particles to help carry the tensile loads imposed by rail vehicles. In the early application of geogrids within the ballast and sub-ballast layers of rail structures, the products were typically used to provide an extension of the roadbed service life. In more re-cent times however, the emphasis seems to have switched, whereby the focus tends to be more on a reduction in the thickness of the ballast layer, or more likely the underlying subballast. The adoption of this approach is intended to maximize “up front” cost savings for the project. In the UK, the approach to roadbed thickness reduction has progressed to such an extent that clear guidance now exists to allow the designer to quantify the reduction that can be attained using geogrid reinforcement; this is provided by Network Rail (the country’s National Rail Authority) in their Code of Practice RT/CE/C/039 (2003).
