Geofabrics
Geofabrics
TrackTex – Solving Mud Pumping for the Rail Industry Worldwide
This article first appeared in the Railway-News Magazine Issue 3 2023.
Since the costly issue of mud pumping was identified by the rail industry, decades of research have gone into developing solutions, which have evolved over time.
Problem areas of ballast contamination in trackbeds cause a real headache for rail operators and contractors alike. But solving the issue often has a considerable impact on day-to-day operations and budgets, due to demanding track possession times and frequent maintenance intervals.
Re-ballasting has often been adopted as a solution. However, this is a short-term answer and over time, the problem returns – again and again. The cost implication of regular, repeated maintenance is significant but can be avoided by employing a specialist solution. There are three targeted methods that have been used over the years to tackle mud pumping:
Sand Blankets
Traditionally, mud-pumping was treated with the installation of a 300mm thick sand blanket. While this proved very effective at preventing the migration of fines, the installation of a sand blanket requires significant excavation – and consequently a large volume of material needing to be imported and exported. This makes for a slow and expensive installation – a challenging exercise to complete within a given possession window.
Geotextiles
As geotextiles were developed during the 1970s, the performance they offered led to the suggestion that they would become the replacement for sand blankets. However, following extensive testing it was established that the pore opening size of these geotextiles was not sufficiently small to prevent the pumping of fines into the ballast. Further research in the 1980s showed that geotextiles could be used to reduce the sand blanket thickness, but not to totally remove it and the associated costs.
Geocells
The stiffening effect created by geocells is designed to stabilise the ballast – which may help prevent pumping. However, without a physical barrier, fines are still likely to migrate into the ballast over time. As with sand blankets, the installation of geocells requires excavation so it’s a slow and labour-intensive process. Future ballast cleaning and tamping works may also be hindered as the geocell sits within the ballast build up.
