Presto Geosystems
Ballast Stabilisation Using Geocells: The Often-Overlooked Importance of Junction Efficiency as a Key Design Consideration
This article first appeared in the Railway-News magazine, Issue 2 2023.
A significant number of research studies have been carried out to investigate the benefits of using geocells in railway trackbed applications.
Combined with an ever-expanding list of successful projects from around the world, the benefits of using geocells in rail ballast stabilisation is welldocumented. Rail operators understand that durable track geometry starts with a solid foundation, and geocells have emerged as a powerful value engineering tool for reinforcing ballast and sub-ballast layers while optimising layer thicknesses.
Many practitioners may not be aware of the critical role that geocell junctions (both mechanical and internal) play in ensuring that the installed system performs in a uniform and consistent manner. In trackbed stabilisation applications, non-uniform junction performance can lead to differential settlement and localised subsidence – which in turn can lead to serviceability issues and a reduction in overall design life. In essence, poor junction performance can nullify all the intended benefits of a geocell system.
This article will succinctly discuss the different types of junctions present in geocell systems, failure mechanisms and test methods, and the concept of junction efficiency as a performance parameter.
Types of Geocell Junctions
There are two types of junctions present in any geocell system: internal junctions, the factory-welded seams that create the interior cells of the panel, located within the body of a geocell panel; and mechanical junctions located around the perimeter of an individual panel, formed during installation when adjacent panels are connected in the field, creating mechanically joined cells along panel joints. Since a primary mechanism by which geocells provide benefit is through lateral confinement of the infill, it is vital that both types of junctions remain intact during construction and throughout the design life of a project.
