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Bridging the gap

GEOSYNTHETICS SURVEY

Specifiers of geosynthetic products believe they incorporate geosynthetics in designs when practical and cost beneficial, whereas suppliers feel there is a 'deep-seated mistrust of new and untried solutions'. Through questionnaires sent to both specifiers and suppliers, Ground Engineering investigates attitudes to geosynthetics, assesses their potential for growth and looks at the factors that inhibit wider use.

GE news standfirst

Specifiers' view

Are geosynthetics used to their full potential?

Specifiers are divided on this question, although the majority of respondents believe there are still untapped benefits.

Darren Russell of Mott MacDonald says: 'Technically there is a lot more to be done with geosynthetics and new and better uses are being developed.

' However, there is a need for a better understanding of the mechanisms involved for many applications. Geosynthetics is not the best solution in all cases and alternatives should not be ignored.'

Ian Thompson, technical director of Weeks Consulting, has wide experience in specifying geosynthetics for landfill applications. He believes geosynthetics are well used in this field, probably more than in other branches of geotechnics.

Peter Whyley of Edge Consultants says knowledgeable designers appear to incorporate geosynthetics in designs when practical and cost beneficial.

Maunsell's Steve Corbet gives a more emphatic view: 'There is still room for increased use to minimise use of 'natural' resources and to improve standards of construction.'

Have you encountered reluctance from a client to adopt a geosynthetic reliant design?

In marked contrast to the experience of the suppliers, only one specifier has experienced reluctance from a client to adopt a geosynthetic reliant design.

'Some clients insist on hanging on to traditional details,' says Corbet. 'Normally this is due to concerns about long-term durability, even when they are reminded of some of the problems which traditional materials can experience - eg Alkali/silica reactions in concrete, accelerated low water bacterial corrosion of steel piles.

'The geosynthetics industry now has a comprehensive set of durability tests available through BSI/CEN and ASTM, to allow the durability of products to be demonstrated.'

Is there sufficient published information in the public domain?

Specifiers want better access to independent case histories, design guides and cost guides. Some expressed concern that most of the information is written by suppliers.

Darren Russell of Mott MacDonald says: 'Generally I think there is enough published literature and suppliers are usually quick to supply data. We do need more data on long-term performance. Estimates of strengths for 120-year design life for some materials is rather speculative at present.'

Once again Corbet has the final word. 'The availability of literature is good, but despite the work in CEN in producing EN Standards, the industry is only slowly getting rid of data and information produced to old standards.

'The real problem will be in clearing out the old literature from specifiers' systems. The proceedings of the International Geosynthetics Society's conferences provide answers to most problems but are little known. The text books available through Thomas Telford should point designers in the right direction if used.

'Because many designers, specifiers, and purchasers are not aware of where to find the information - and even when they do find it don't understand it - I have launched the Geosynthetics Helpline.' [see news this month]

What factors inhibit wider use of geosynthetics?

Inhibiting factors identified by specifiers include:

Lack of knowledge.

Poor coverage in civil and geotechnical engineering university courses (IGS is producing a set of short mini lectures which will be made available to educators - see news).

Long-term performance is the key to building confidence and this will only come with time as more case history data is available.

Reluctance to use materials and methods of construction which are seen as new or novel, despite the use of geosynthetics in engineered construction for up to 25 years, and that the practice of 'soil reinforcement' can be traced back to Babylonian constructions.

Landfill design is set in licences and working plans; it might not be in the client's immediate interest to seek approval for a novel approach.

What are the likely main growth areas for geosynthetics in the next decade?

Growth areas identified by suppliers:

Railway applications for track-bed improvement and slope stabilisation measures.

Geocomposites in contaminated land with applications for gas/water control and barriers.

Increased use of reinforced soil as an alternative to conventional retaining walls, particularly with increased confidence from long-term performance and as confidence grows in block wall systems used at greater heights.

Increasingly geosynthetics are used in soft (and not so soft) ground applications to speed construction.

Any situation which reduces the volume of high cost, good quality granular materials.

More use in landfills to isolate smaller volumes but possibly more toxic wastes from the environment.

Multi-layer systems refined and more use made of GCLs in combination with other geomembranes and geotextiles.

More use of high modulus reinforcements in pavement construction, which need to be combined with revised pavement design procedures.

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