A STRENGTHENING MARKET

Publication this month of the new UK code of practice on strengthened-reinforced soils will, industry experts predict, give the already expanding geosynthetics market an additional shot in the arm.

The new code is described as a watershed by Bernard Myles, chairman of the BSI committee on geotextiles. 'It has taken 10 years to bring about. Publication of BS 8006 should take away any excuse for engineers not to use geosynthetics in the future,' he said.

The new code, BS 8006: 'Strengthened/reinforced soils and other fills', is just one in a rush of new regulations covering geosynthetics (a term which covers geotextiles, geomembranes and geogrids) which is expected to boost the use of the technology.

Despite the downturn in construction output over recent years, market usage of geosynthetics has grown as engineers have found new applications, often at the expense of 'hard engineering' solutions. Areas such as asphalt overlays, landfills, basal reinforcement, geocomposite drainage systems and high strength geogrids have seen geosynthetics sales expand.

Estimates of the current UK market for geosynthetics vary widely, with between 40-50 million m2 of standard geotextile laid annually, worth around œ40 million. Having remained fairly static during the recession, growth has returned at around 5% overall, although some specialist sectors, such as products for soil reinforcement are enjoying higher growth rates but from a smaller base. Prices are also said to have hardened considerably in recent years.

'Road construction is dominated by government policy, which has meant that conventional geotextiles have not enjoyed the same level of growth in the UK as the specialist sector,' said Chris Lawson, marketing applications manager at newly-named UK manufacturer, Terram, which was aquired by BBA in January.

Recent growth in the market has been helped by the publication last year of the Highways Agency code for the design of over steep reinforced slopes, HA68/94, and by the use of geosynthetics on high profile projects such as the widening of the M25.

'These have given an impetus to soil reinforcing, and hence geosynthetics,' said Steve Corbet, vice chairman of the International Geosynthetics Society in the UK. 'Clients are becoming aware that the technique is effective, economic and gives a more acceptable finish than heavy engineering solutions. They are therefore using it in places where they were reluctant to do so in the past.'

When it is published, BS 8006 is expected to supersede the Highways Agency's existing HA68, which is considered by many to be a relatively simple and rather prescriptive document. Ignorance of geosynthetics and relevant design techniques is still considered a problem in the UK, with brand specification widespread. The new code will be more instructive than the existing code, concentrating on the basics of geotextile design, and giving engineers the confidence to specify a geotextile solution to a problem.

Myles believes the new code will be a turning point in the development of the sector, as, for the first time, it will give consultants and contractors access to independent product appraisal. Up until now, specifiers have been largely reliant upon the information supplied by manufacturers, based upon widely varying test and appraisal methods. Under the new code, clients will be able to make comparisons across products and applications, using failure and, importantly, serviceability criteria.

The production of new regulations at home has been spurred by the activities of CEN, the EU standardisation committee, whose geotextiles committee, TC189, will introduce the first draft of the standard test methods and uniform appraisal methods some time this autumn.

After a slow start, the UK has been at the forefront in drawing up the new European test standards for geosynthetics. Once the significance of the agenda being set by other European countries, notably Germany and France, was recognised by bodies such as the Highways Agency, they began taking geotextiles seriously and became enthusiastic contributors.

As a result, it is expected that a significant proportion of the UK's BS 8006 will be taken on board during the drafting of the new European document. 'In the UK we came to consider our standard fairly late, so we could anticipate the harmonised situation when drafting our own. Only minor changes to UK codes are therefore anticipated when the CEN regulations are implemented,' said Myles, who heads the UK geosynthetics delegation to the EU.

One proposal, put forward by Germany and the UK, but voted out by the other members, was for a classification system to cover geosynthetics. The UK proposal was much less prescriptive than the German option, which linked applications and materials. The UK system would classify products according to grades, leaving the engineer as the final arbiter in the choice of which material to use in a given situation.

The development of the UK classification system is now well underway, and should be ready by the end of the year. It is anticipated that some sort of classification system, based on the British approach, will eventually be adopted throughout the EU. As a result, the BSI and its German counterpart are liaising to ensure the two developing systems are aligned.

Such a system will be good news for the user, enabling direct comparison of products' properties and relative costs. 'The vast majority of geosynthetic uses are simple applications and classification will remove the mystique of specification,' predicted Myles. 'It would enable UK designers to ensure works are built to their own specification,' said Corbet.

This groundswell of new legislation will have a fundamental impact on the proliferation of geosynthetics, which are developing in numerous directions.

Growth in design and build and design, build and operate schemes, mean that contractors are eager to consider any technique which offers a faster, cheaper solution, especially those which utilise the materials already on site.

'Design and build contractors who have previously gained experience of working with geosynthetics specified by consultants, have quickly realised their potential for saving time and money and have made a bee-line for the right suppliers, especially those who can offer design solutions,' confirmed Peter Langley, marketing manager at geogrid manufacturer, Netlon's civil engineering division. However, he notes that, while geosynthetics are growing in the UK, they are not yet growing at the same rate as in overseas markets, such as North America.

Not that geosynthetics should be seen as a panacea for all engineering problems. For example, tests on asphalt overlays, by the Department of Transport, TRL and county highways agencies have so far proved inconclusive. When laid in asphalt as a road repair system, geotextiles perform well as a crack inhibitor in the medium term. However, accelerated tests indicate that the working life is not prolonged by the method, casting doubt on long term cost effectiveness.

Corbet highlights another growth area, that of geosynthetic reinforced modular pre-cast concrete block walls. These interlocking blocks were originally developed to form low, architectural walls of around 2m high. However, when the block face is tied into layers of geosynthetic laid in the backfill, walls of up to 20m can be constructed.

The technique is popular in the US and Canada, and several examples have already been erected in the UK, although not to this height. 'With this new technology, you have to take clients along gently,' said Corbet.

Another area attracting attention is the use of geomembranes as a containment barrier in waste disposal and in the treatment of contaminated land.

Geosynthetic clay liners are popular in North America where they are often used as self-sealing secondary liners, which are much quicker to install than traditional techniques. While their use is becoming more accepted by local authorities and licensing agencies in the UK, firm, clear guidance on their use is still awaited.

Estimates of the extent of contaminated land in this country vary from 100,000ha to 200,000ha. Redevelopment costs are estimated at œ500 million a year, with an overall price tag of some œ20 billion. The method of treatment currently favoured in the UK is that of containment, with long term research being undertaken by the BRE and CIRIA into the durability and performance of products such as bentonite cut-off walls, as well as geomembranes.

Information papers on the design of such systems should be published in the next few months.

Committees at the BSI and CEN are also considering the problem and a European directive on waste tip liners is expected some time in 1996. However, it is not anticipated the this legislation will be as important in forwarding the cause of geomembranes as the new BS 8006 will be for geotextiles. 'The use of geosynthetics in this field is not yet so established,' said Myles, 'but the directive will bring to light certain applications not now recognised.'

There is little doubt that the spread of geosynthetics in the UK has been hampered by the lack of standards and workable codes of practice. However, nothing concentrates the mind like impending deadlines, and the work of the CEN has forced the Highways Agency, and other bodies to give serious consideration to what they want from geosynthetics, ensuring their wider acceptance and greater use.



There is a one-day symposium on 18 May at the Institution of Civil Engineers, London - 'The Practice of Soil Reinforcing in Europe'. Contact Peter Griffiths on 0171 839 9953.