Rail track is supported by ballast foundations, which can become unsettled as many trains cross over it, leading to growing deterioration in ride quality for freight and passenger traffic. Remedial maintenance work is then required, costing an estimated £460 million annually in the UK, resulting in the all-too-familiar service delays and cancellations.
The University of Nottingham team was able to increase the maintenance cycle through the use of Geogrid, a lightweight plastic mesh that Network Rail were keen to trial. The team modelled the interaction between the foundation ballast and the Geogrid to determine optimal grid size and predict the most effective location. The research team worked closely with commercial partners Tensar International, who later licensed the grid design for commercial sale.
The use of Geogrids is now approved for general track use, and for use under the parts of the rail network that are the most difficult to maintain to a high standard – switch and crossing installations. Network Rail was involved in early stage trials of the design, later integrating it into their track maintenance procedures. Since the inception of systematic use of Geogrids in 2008, Network Rail has saved around £3.2 million in maintenance costs with predicted ongoing savings per year of £1 million. This stems from a typical doubling of the track maintenance cycle time, with further impact on increased availability of track time, providing increased service reliability and consistency.