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TENAX solutions for railways


geogrid reinforcement of railway ballast
Vinkovci/Tovarnik, Croatia
Geogrid reinforcement of railway ballast.
185,000m2 of geogrid have been installed for Croatian Railroad.


The repeated rapid passage of trains in very brief intervals of time, apply dynamic loads to the soil resulting in very intense compression and decompression cycles.


Thus railway foundations are being subject to constant fatigue stress leading to frequent and expensive maintenance requirements. Although these maintenance costs are high, by far the most expensive cost factor is the reduction in revenue caused by the disrupted services.

TENAX geogrids are extremely effective in reinforcing unbound granular layers in roads and other trafficked areas such as, car parks, airports and docks.


The use of geogrids in ground stabilization allows the overall construction depth to be reduced. This saving on materials and excavation also provides safe working platforms that meet economic and environmental constraints.

By incorporating TENAX RailGrid (LBO 370) within railway construction layers, it is possible to combine major cost savings with considerable performance benefits at both the ballast and sub-ballast levels.

When ballast or sub-ballast granular material is compacted over TENAX geogrids, stone particles partially enter the apertures of the grid and are eventually "locked-in" to create a strong and positive interlock along the plane of the geogrid.


This locking mechanism enables the grid to resist horizontal movement of the stones which improves ballast performance and reduces railway ballast settlement.



Over time the constant movement of traffic over the track causes the railway ballast to eventually deteriorate with voids forming within the ballast structure. Often, from the track side, sleepers can be clearly seen bouncing up and down as the wheels pass over them.


This excessive movement is dangerous and so the voids need to be filled and re-compacted to give a firm base for each sleeper. In other areas, loose broken fragments fill the voids within the ballast matrix reducing the drainage characteristics of the railway construction layers.

Ballast tamping operations are then carried out to maintain track line and levels. Tamping machines are designed to vibrate the ballast and force it under the sleeper. These combined actions cause the ballast to form a close matrix which can support the track effectively once again.


However, continuous tamping operations can cause further particle breakage and eventually the ballast is spent and has to be replaced.


It is therefore desirable to increase the ballast life so that tamping requirements are reduced resulting in less maintenance activity, less disruption to operations and increased savings for the rail operator.

TENAX RailGrid LBO 370 geogrids are used to limit the deformation in ballast layers by providing interlock along the plane of the geogrid.


This reduces the formation of voids and therefore prolongs the life of the ballast thereby passing on significant cost benefits to the rail operator.



TENAX geogrids are also used in new line construction over poor subgrade. Their use within the sub-ballast allows substantial reductions in the required layer thickness due to the reinforcing effect.


This can in addition often allow the depth of excavation of poor formation soils to be reduced with less disposal costs. Furthermore, the geogrids can be used with recycled aggregate such as crushed concrete.

The economic and environmental benefits of using Tenax in the sub-ballast have been widely experienced over recent years, particularly in the construction of new rail corridors across mainland Europe.

ballast reinforcement
Ballast reinforcement
Geogrid improves stiffness of ballast and provides lateral confinement of coarse aggregate.


ballast reinforcement
Sub-ballast reinforcement
Geogrid limits deformation of overlying ballast layer and distributes stresses along the plane of the geogrid.

geogrid to increase ballast performance
geogrids for railways
Midgham, England
TENAX RailGrid installed to increase ballast performance and reduce maintenance frequencies.


TENAX RailGrid LBO 370
Resistance to abrasion according to EN ISO 13427
  Control Exposed
at Maximum
at Maximum
MD 2302,2 13,3 2280,8 12,7 99,07 95,63
TD 2664,0 12,9 2521,0 12,1 94,63 93,64
MD: machine direction
TD: transversal direction


The benefits


Key benefits when using TENAX RailGrid geogrids within railway foundation layers:


Improved ballast performance allowing for consistent high speeds to be achieved.
Improved stabilization of track foundation layers.
Reduction in the rate of ballast degradation and settlement.
Reduction in overall maintenance cycles.
Reduction in tamping operations, thereby increasing the life of the ballast.
Reduced excavation and use of expensive imported fill.

TENAX Rail Grid geogrid


TENAX RailGrid geogrids are manufactured from a unique process of extrusion and then bi-oriented to enhance their tensile properties.
They are manufactured from polypropylene and produced with high tensile stiffness in both longitudinal and transverse directions allowing load to be resisted at very low strains.


RailGrid interlock


They are designed specifically with large rigid square apertures having an optimum mesh size of 65 mm therefore maximising mechanical interlock with the railway ballast.
Bi-oriented geogrids provide an effective way of reducing the rate of ballast settlement over soft subgrades. Independent trials have confirmed that it is the stiffness and the size of the geogrid apertures that determine the structural performance of pavements.

TENAX geogrids provide an extremely cost-effective solution for the reinforcement of ballast over soft subgrade bringing significant benefits to the railway engineer.

Research and testing
It is well known that railway ballast is one of the most aggressive granular materials for geosynthetic rail applications, composing of large sized, angular stones. It is therefore important to confirm the performance of the geogrid after installation by determining the effective reduction in tensile properties due to this possible damaging action. A very simple index test, “Abrasion Damage Simulation” (EN ISO 13427) can be used to give an indication of these abrasion effects. Tests performed on TENAX RailGrid at independent laboratories have shown residual strengths in excess of 90% in both directions, thus clearly demonstrating the suitability of the geogrid for reinforcement of the railway ballast.

RailGrid certification and approvals

Certification and approvals

TENAX RailGrid LBO 370 is certified by European railway authorities such as Network Rail, UK’s national railway authority, and Delta Rail, The Netherlands’ national railway authority.

network Rail
Delta Rail

TENX RailGrid for railways

geogrids for railways

geogrids for railways
Extensive research continues on a
live site involving instrumentation
of the TENAX geogrids.



TENAX GT geocomposite for drainage


TENAX GT geocomposite

With TENAX GT Tenax bi-oriented geogrids are also available as a composite material where a geotextile is bonded to the geogrid.
In addition to the reinforcement function provided by the geogrid, the geotextile component offers additional separation and filtration functions where necessary.

track ballast renewal

track ballast renewal

Mantgum, The Netherlands
Friesland track ballast renewal was completed using a ballast-cleaning train running at 3 m/s simultaneously placing a geocomposite to stabilise the ballast/subgrade interface and to minimise the upward movement of subgrade fines.

geocomposite TENAX TENDRAIN for railway track drainage


Drainage of railway tracks is essential to ensure acceptable track performance. The cost of maintenance or, conversely, the deterioration of track components is directly impacted by the condition of the drainage system.
Excess water can create a saturated state in the ballast and sub-ballast, causing premature failure of the ballast system leading to frequent repair operations and significant increases in track maintenance costs.
Achieving proper drainage is not simply a matter of excavating a cross trench and letting water out of the track but it is reliant on providing a free draining base.
The use of TENAX TENDRAIN geocomposites over traditional methods of drainage can provide a rapid and cost effective solution for the requirements of sub-surface drainage in railway tracks. Instead of the installation of expensive granular layers to facilitate drainage, TENAX TENDRAIN geocomposites can be used to collect water filtering down through the railway construction layers as well as capturing water seeping upwards from the subgrade as a capillary break.

capillary break solution for railway


TENAX TENDRAIN can be installed between the foundation soils and the upper layers of inert material providing a stiff separating function capable of supporting high compressive loads whilst preventing any accumulation of water thus achieving a well-drained and dry base with a longer design life, higher mechanical properties and with no water inclusion.

The benefits

Benefits of installing TENAX TENDRAIN include:
A major cost saving when compared with traditional filtration methods e.g. imported granular filtration blankets.
An improved stiffening and overall strength of ballast and sub-ballast layers due to better control of the water.
A reduced potential for hydraulic pumping of fine soils from subgrade up into the sub-ballast and ballast.
A reduced potential of excess pore water pressure build-up under cyclic loading.
A reduction in ballast degradation from slurry abrasion, chemical action and freezing of water.



Research and testing
A critical measure for the operational life of a drainage geocomposite is the reduction in thickness when compressive stresses are applied to its surface as this thickness reduction ultimately affects the drainage capacity of the product.
After initial elastic deformation occurs, the deformation related to creep phenomena is measured through compressive creep testing to EN 1897 standard.


When tested in accordance with EN1897, the chart shows the drainage core of TENAX TENDRAIN geocomposites as having a curve that is almost flat after 10,000 hours. This means that the residual thickness after this period tends to be constant, and that no further deformations will occur, showing the product is able to maintain its hydraulic capacity in the long term under high compressive stresses.

Tenax geocomposite for railways

Padova-Mestre, Italy
Capillary break layer under the new high speed train line Milan-Venice in the Venice-Mestre area.


TENAX Corporation
4800 East Monument Street, Baltimore, Maryland 21205, USA

Phone: 410-522-7000 • Toll free phone: 800-356-8495
Fax: 410-522-7015 • Toll free fax: 877-836-2987

Manufacturer since 1987