Geosynthetics in Railways

Right across the world, geosynthetics are used to aid in not only the construction of railways but more importantly, to prolong the life of the track and reduce the need for maintenance.

Some of the key reasons for using geosynthetics are:

• Separation / filtration of the ballast and sub-ballast/capping layers

• Reinforcement of the ballast

• Stabilisation of the subgrade

• Reinforced slopes and embankments

• Prevention of Mud-Pumping

• Erosion control of embankments

• Waterproofing and drainage

With the above applications, materials like geotextiles, geogrids, Hydrotex (geotextile composite) and High-Performance Turf Reinforcement Mats (HPTRM’s) are some of the materials used.

Below are some examples of how these materials are used.

Separation / Filtration

Using geotextiles is widely known, however, within a rail application where there are dynamic loads in place, there is the added risk of abrasion of the geotextile taking place. To reduce the risk of this happening, the best practice adopted around the world is to use staple (cut/short) fibre-based geotextiles like Profab®.

As the fibres are already being cut, if abrasion occurs, it will be localised and won’t spread throughout the roll of material, as it will with geotextiles made from continuous filament.

Ballast Reinforcement and Subgrade Stabilisation

Ballast reinforcement is achieved by using geogrids like Secugrid®. The ballast interlocks with the geogrids to reduce the movement and ballast degradation, while enhancing the performance.

It can equally be combined with a geotextile, known as Combigrid®, to stabilise the soft subgrade and sub-ballast. This improves the baring capacity, provides the opportunity to reduce the thickness of sub-ballast, while reducing the stress on the subgrade and preventing differential settlement.

Both these materials have undergone extensive research at University of Wollongong with the paper available upon request.

Prevention of Mud-Pumping

Mud pumping is an issue of the clay base taking on too much water and turning the clay into a liquid slurry. This then causes the ballast to slip and move as the slurry migrates north. The traditional way this has been combated has been the use of a sub-ballast or capping layer which is both timely and expensive to install.

Now with the use of Terram Hydrotex® and specialised nonwoven Geocomposite, you can remove the need for the capping layer all together due to its very small pore size of the material. It separates the water from the clay, allowing the clay to dry out while pushing the water to the side of the track.

Fully researched by Birmingham University 10 years ago, and more recently the University of Wollongong and University of Technology Sydney to calculate the required material in association of the ground conditions and types of trains operating the line.

Reinforced Slopes and Embankments

Reinforcement of surrounding embankments is another critical function of geosynthetics. Utilising materials like our ACEGrid® and ACETex® high strength geosynthetics enables you to construct near-vertical embankments or equally stabilise existing embankments to ensure the highest level of safety around the track is achieved, while equally reducing the amount of soil that needs removing for the new track construction.

Erosion Control of Embankments

Erosion control is a critical part of all embankments along the side of the rail track. Ensuring no erosion takes place, which can result in big delays to operations while repairs take place, is also a critical aspect of keeping the line safe at all times.

Utilising our highly UV stabilised Pyramat® range and Armormax® anchoring system enables you to both permanently control any potential erosion while equally stabilising the surface of the embankment for a design life of >100yrs.

It equally can enable you to establish controlled vegetation in areas that would otherwise struggle.

Finally, with the lasted fire-resistant technology incorporated, it means that should a bushfire event occur, the material and embankment will still maintain and keep working.

Geosynthetics are revolutionising railway construction and maintenance. From extending track life to reducing mud-pumping and erosion, these innovative materials offer significant benefits.

Contact us today to discuss your specific needs and learn how geotextiles, geogrids, and other solutions can optimise your railway project!