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Putting geotextile tests on common ground

   
 
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Geotextiles.

Standards research may not be glamourous but its economic impacts are immense. A recent European Commission study found that our geotextile manufacturers were missing international market opportunities because of the lack of accepted standards. A research team of experts analysed tests for nine different properties and put forward a set of 13 suggested standards to the European Committee for Standardisation.

 

Geotextiles have four main functions: reinforcement, separation, filtration and drainage. Civil engineers have been using them since the 1960s to build roads, canals, railways, tunnels and dams. The ideas behind them are not new, however. In biblical times, reeds reinforced clay to prevent erosion along the banks of the Tigris and the Euphrates. Today, geotextiles find their way into environmental projects, controlling coastal erosion, keeping waste safely within landfills and improving land use - steeper slopes require less land for embankments.

Technology has moved on and today's geotextiles are manmade polymers that have been woven or extruded. Polypropylene, polyester and polyethylene are the most frequently used materials. Non-woven varieties are the most common and here, a web of fine fibres is laid out and then bonded by heat. The production process is relatively flexible and manufacturers specially design geotextiles with properties that will suit their use, whether that is to separate soil, lay a pond or build up banks.

Demand for research

About a 1,000 square kilometres of these geotextiles are manufactured globally each year and producers are always keen to expand into more international markets. A study conducted for the European Commission found that the principal obstacle to trade was a lack of common standards for production and testing of geotextiles.

Aiming to create a single market for all types of building materials, the Commission introduced the Construction Product Directive, including geotextiles. To support the Directive, the European Committee on Standardisation (CEN) set up a Technical Committee to set standards for geotextiles. Selecting a single test method from the existing national standards, or designing a new one, is not easy. One country may use an obscure test that no one is familiar with, while other tests may give random and variable results for no apparent reason. Some countries may not actually have a standard method. For several methods, the committee soon reached a stalemate which could only be broken by actually testing each of the methods for their relative merits and shortcomings.

With the financial support of the Measurements and Testing programme, a project to develop a comprehensive set of test methods began in 1994.

A total of 31 different organisations from 13 European countries rigorously evaluated nine tests that had been identified as needing further development. These tests covered a lot of ground, from filtration opening size and hydraulic permeability through to friction testing and creep. Artificial weathering by exposure to UV light and resistance to biological and chemical action were also on the testing agenda. For some of the tests, a number of different methods existed and these all had to be scrutinised.

Ground-breaking research

"A two and a half year work programme was approved, starting with detailed research tasks and culminating in international trials," explains John Greenwood, the project coordinator from ERA Technology, an independent contract research and consultancy organisation in the UK. "We had participation from many university, industrial, government and independent groups. Many manufacturers donated materials."

With so many experts on board, keen observation meant it was sometimes easy to spot the reason for result variation, thus saving hours of committee discussion about which results are correct. As the study progressed, the team modified test methods until they were satisfied that the method could be used in a standard. "The Committee has now proposed a set of European Standards on geosynthetics for approval by CEN, including 13 proposals that have had support from the SMT project.

Towards a unified market in Europe and globally

Among these are tests previously used in national standards tests with improved procedures and some completely new tests," continues Dr Greenwood. These standards form part of a range of formal requirements and associated test methods whose use will be mandatory throughout the European Union. A producer will only have to perform one set of these tests to put his or her product on the market, thus lowering trade barriers within the EU. This more straightforward testing regime reduces testing costs which are always passed on to the consumer eventually.

The knowledge generated in this project sparked interest from across the Atlantic and has led to an exchange of information agreement giving European researchers access to the results of parallel work in America. On the world stage, the methods are also being put forward as international standards. In the not too distant future, it should be possible for only one set of tests to be needed for European manufacturers to export their geotextiles and their expertise around the world.

 

 

Project Title:  Research and Intercomparison test necessary for the harmonisation of standards in geotextiles

Programmes: Measurements and Testing
Contract Reference: MAT1-CT94-0019

Cordis DatabaseFor more information on this project,
go to the Cordis Database Record

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