Railway Project – Telegaon Case Study

For a railway project at Telegaon, Maharashtra, Ocean supplied Ocean Non-Woven Geotextile-300gsm and Ocean Geogrid-30kn for the track substructure. The two products work together under the track: the geotextile keeps the layers separate and drained, and the geogrid holds the granular material in place.

Railways are among the cheapest ways to move freight and passengers, and as traffic and train speeds rise, so do the cyclic stresses on the substructure beneath the track, mainly the ballast and sub-ballast layers. Research into railway substructures over the past decades has consistently found that geosynthetics help build stronger, safer and more economical track. They are used in rail construction for:

• Soft subgrade stabilisation, as an alternative to excavation and replacement
• Ballast reinforcement
• Separation and filtration to keep the sub-ballast and capping layers stable
• Basal reinforcement of rail embankments
• Reinforced steep slopes
• Waterproofing and drainage

Product

• Ocean Non-Woven Geotextile-300gsm
• Ocean Geogrid-30kn

Quantity

• 12000 sqm
• 12140 sqm

Location
Telegaon, Maharashtra

Problem

Ballast spreads the train load down to the sub-ballast, holds the track in line and lets water drain away quickly. The sub-ballast reduces the stress passed to the soil below and acts as a filter that stops subgrade soil migrating up into the ballast. Under continuous traffic, though, unbound ballast spreads sideways and its particles break down, and both effects lead to track settlement.

Excessive ballast deformation and degradation pull the track out of alignment. The railway then has to impose speed restrictions or carry out costly maintenance such as frequent tamping. This is the reason railways around the world have started using geogrids to stabilise track, compared with the highways sector where geogrids have long been standard.

Solution

Geogrid. Geogrids are usually placed at the bottom of the ballast layer, at the ballast and sub-ballast interface, where they do not get in the way of tamping and other track maintenance. Ballast stones lock into the grid apertures, and the grid restrains them from moving sideways. Less lateral spreading means less vertical settlement and slower ballast breakdown. For ballast, the grid aperture needs to be large enough for the stones to interlock, so large-aperture grades are generally chosen.

Geotextile. Non-woven geotextiles are placed at the top of the subgrade or formation. They separate subgrade soil from the granular layers, filter water out of the formation while holding fines back, and prevent the mud pumping that fouls ballast on wet, fine-grained soils. Unlike the geogrid, a geotextile does not restrain the ballast; its job is to keep the layers clean and drained.

Used together, the two products address the main causes of track settlement and reduce how often the line needs maintenance.