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Railways

Erosion Control

Frequently Asked Questions

What is a Geotextile?

permeable highly durable synthetic fabric general used in Civil Engineering and Building projects such as road and car park construction to stabilise loose soil and prevent erosion. TERRAM geotextiles are highly permeable nonwoven needle punched and thermally treated synthetic fabrics made from polypropylene used to separate, filter, reinforce, protect, or drain engineering soilsTypical uses include preventing intermixing of granular sub-base and subgrade layers, drainage and bedding materials. TERRAM geotextiles help reduce wastage/loss of expensive imported granular materials, improve structural performance and extend the life of the pavement/road/rail track. 

What is a TERRAM Geotextile used for?

TERRAM geotextiles are predominantly used for separation and filtration of fill materials preventing intermixing and extending the service life of unbound materialsTERRAM geotextiles can also be used to provide puncture resistance and reinforcement in certain applications. 

What is the difference between a woven and nonwoven (TERRAM) geotextile?

A woven geotextile is manufactured from continuous filaments or strips of synthetic material which are woven together to form a uniform sheet. A woven geotextile has a very uniform pore size which varies under load making them less suitable for filtering anything other than clean single sized soils/fills. Nonwoven geotextiles are a tangled web of fibres mechanically and/or thermally bonded together to form a non-uniform random web. Nonwoven TERRAM geotextiles have a wide range of pore sizes which make them ideally suited for filtering many different types of fill materials including well graded materials even under varying load conditions.

Are TERRAM products approved by Network Rail and TFL?

All TERRAM PW (Permanent Way), Standard Geotextiles and Hydrotex products hold Network Rail Acceptance certificates and have associated PADS numbers. TFL (Transport for London) and Network Rail require that all suppliers use of a qualification scheme called RISQS (Railway Industry Supplier Qualification Scheme). TERRAM (trading as Fiberweb Geosynthetics Ltd, part of the Berry Group) are registered with RISQS.

Are TERRAM Geocells permeable?

Yes, TERRAM Geocells are manufactured from 100% permeable nonwoven geotextile fabric allowing ground water to pass through the cell walls rather than cascading over or underneath causing soil erosion.

What are the benefits of a TERRAM non-woven geotextile Geocell vs HDPE strips?

TERRAM Geocells are much more flexible and easier to handle than cells made from HDPE (High Density Polyethylene) strips. TERRAM Geocell panels easily match the ground contours ensuring continuous erosion protection rather than bridging over depressions in the surface. The fully permeable fabric of TERRAM geocells ensures fill within the cells remain well drained reducing the risk of soil saturation & erosion. The non-woven geotextile material does not crack or split unlike stiff & brittle HDPE strips. 

What grade of Geocell do I need on a slope?

Generally for slopes up to 30 degrees grades 35/10 & 35/15, for slopes between 30 and 45 degrees grades 25/10, 25/15, 22/20. Please see the TERRAM Geocell erosion control SDI (specification, design and installation) guide for more details. 

Can TERRAM Geocells be used to form retaining walls?

Yes, TERRAM geocells can be used to form retaining structures although this is not an application area that we actively promote in the UK market due to historic lack of demand. Different grades of TERRAM Geocells can be manufactured specifically for retaining structure applications but are made to order and there is a minimum order quantity. 

Can I cut Geocell panels?

TERRAM Geocells are manufactured from strips of stiff but flexible nonwoven geotextile material chemically bonded at the joints to form honeycomb panels with cells ranging in diameters from 220mm to 350mm and strip widths (panel depths) of 100mm to 200mm. Single layers can be easily cut by hand with safety knives or sharp scissors with a downward action close to the joints. Wear appropriate personal protective equipment such as gloves and eye protection.