TracktexTM helps keep rail services moving
The Australian Rail Track Corporation Ltd (ARTC) manages the rail network in NSW which moves a range of commodities including general freight, coal, iron ore and agricultural products, as well as providing access for interstate and inter-city passenger services.
A major problem on the network is that axle loads north of Dartbrook are limited to 25 tonne, however coal producers have approved a programme of track rehabilitation to increase this capacity to 30 tonne axle loads and to minimise speed restrictions in affected sections of the track.
Geofabrics have recently introduced a new product specifically targeted at rail maintenance applications. TracktexTM is specifically manufactured to address “Erosion Pumping Failure” and is a composite material consisting of a unique micro-porous filter, sandwiched between two layers of bidim® nonwoven high strength protection geotextiles.
When installed at the ballast interface, TracktexTM prevents water penetrating into the underlying deposits but allows subgrade pore-water pressure to dissipate by capillary action. This prevents fine soil particles migrating upwards to contaminate the ballast and retains the soil in situ thereby preventing depressions forming. The composite geosynthetic layer also conforms to the profile of the formation which minimises the potential for pockets where slurry could accumulate.
The ARTC in conjunction with Geofabrics discussed TracktexTM as an ideal solution to reduce the adverse effects of pumping fines at this site. This was the first time that TracktexTM was incorporated into maintenance works in NSW.
The ARTC also identified that due to the poor bearing capacity of the underlying alluvial soils, they decided to also install Tensar® TriAxTM TX170 geogrid to improve the bearing capacity and minimise any differential settlements once the reconstruction was complete.
Tensar® geogrids improve the bearing capacity by stabilising the overlying aggregates by interlock of the ballast into the apertures of the geogrid. This not only reduces lateral movement but also any vertical displacement which would affect the rail geometry.
Tensar® TriAxTM TX170 was placed directly over the TracktexTM composite layer to stabilise the overlying ballast.
The combination of TracktexTM and Tensar® geogrids provide an excellent solution for a number of major rail track issues, namely erosion pumping and poor bearing capacities.
The ease and speed of installation during a track possession has a cost benefit both in construction cost as well as reducing shut-down duration times.
The ARTC will continue to monitor the performance of this section of rehabilitated rail near Ironbark Creek, however Geofabrics are certain that major benefits will be achieved in reliability, safety and overall performance of track.