A geosynthetic provides one or more of four functions when used in track-bed construction: Separation to maintain the integrity of adjacent soil types i.e. prevent intermixing. Filtration to prevent leaching of soil particles. Drainage to allow the free passage of water. Reinforcement to provide additional strength.

Preventing Clay Pumping

Placement of a sand blanket is time consuming and time is of the essence when working against the possessions’ clock.

Replacing a sand blanket entirely
Manufacturers have continued to develop and evaluate likely candidates for a sand-blanket replacement knowing that the ideal product would have to be:

• Quicker to install
• Lower in (installed) cost
• More readily available 
• More environmentally friendly

Fiberweb Geosynthetics recognised that its own development needed to be focused on the filter function as PW1 alone is not capable of preventing the passage of the smallest clay/silt particles. Fiberweb plc has a great deal of expertise in non-woven filters and this became available when Terram Ltd was acquired by
Fiberweb plc.

Fiberweb developed a filter that was more than capable of preventing the passage of the smallest clay and silt particles. The only complication was that these filters are not particularly robust and would not survive the rigours of track-bed use on their own. The solution was to sandwich the filter at the centre of two robust layers of geotextile to protect it from potential damage. The result was the Hydrotex range of geocomposites.

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TERRAM Hydrotex geocomposite for preventing track-bed clay pumping
TERRAM hydrotex used on clay soild, replacing the need for a sand blanket
TERRAM Hydrotex has a micro-porous fine filter protected between two robust filters