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Ground Engineering

The UK national soft clay test-bed site at Bothkennar is to be sold by the present owner, the Engineering & Physical Sciences Research Council. Should Bothkennar be saved for the nation? If so, how? David Muir Wood initiates discussion to identify an appropriate and satisfactory future for the site.

A task force of the Science & Engineering Research Council reported in 1981 on the desirability of the SERC developing facilities for the full- scale geotechnical testing necessary to reproduce those extra special factors associated with the depositional history - insitu fabric and structure, and natural - variability of real soils. Peter Wroth and George Milligan, geotechnical co-ordinators for the SERC in 1983, plan- ned a soft clay testbed site to complement the stiff clay and glacial till sites used by the Building Research Establish-ment and others to study insitu test procedures and construction

possibilities. The site at Bothkennar was purchased by the SERC in 1987, beating competitor sites around the UK through the availability of an appropriate area of land, and possession of an uncomplicated profile of 20m of soft saturated soils.

Since its purchase, the site has been used to study, among other things, long term downdrag on piles, behaviour of CFA and jacked piles, performance of lightly reinforced unpaved roads, and short and long term performance of shallow foundations with and without stone column reinforcement.

However, the importance of Bothkennar rests especially on the site characterisation carried out in 1989 (and sporadically since) and reported in a special issue of Gotechnique in 1992 which makes it, arguably, the best studied undeveloped site in the world.

The site is an 'archive' where, at any time, anyone can come to try novel testing or construction techniques in the certain knowledge that all the supporting testing needed to define the properties of the soil at any level of sophistication has already been performed. If the long term performance of geotechnical structures is uncertain, tests at Bothkennar can be revisited over many years or decades with the confidence that site conditions are unchanged.

In 1994, just prior to the reorganisation of the research councils and the formation of the EPSRC, a review of the potential for future work at Bothkennar was produced by a team led by David Hight of GCG. This review considered the opinions of researchers throughout the world, and proposed a strategy for the performance of generic full scale tests at Bothkennar to be driven by a 'soft clay champion. However, the problem with Bothkennar has always been that, although there is much interest in the site nationally and internationally, the levels of funding that need to be generated from public and private sources to cover the costs of properly instrumented full-scale testing are very high and the level of activity over the past decade has been low.

For the EPSRC, Bothkennar is something of an anomaly. It is a lightly used facility, has no great monetary value - low grade agricultural land in the flood plain of the Forth - and costs very little to maintain annually, by comparison with the overall EPSRC budget. Other large scale test facilities originally funded by the SERC, such as the Flood Channel Facility, have passed into the private sector, with continuing university access guaranteed while the new owners actively manage and market them. Treasury rules do not permit the EPSRC to retain unused resources, even if the savings in site characterisation costs in occasional field work proposals at a series of new test sites would easily cover the annual costs. Research activities at Bothkennar have always been funded in competition with other research across the whole SERC/EPSRC portfolio. For the future, the minimum required to preserve the site is an owner, a source of funding sufficient to cover basic costs (£5,000-£10,000 per annum for modest site presence together with building maintenance and services), and a mechanism to guarantee and assist access from appropriate researchers. Can the geotechnical community find and sustain this?

The dilemma for the geotechnical community is that - dare I say it? - the purchase of Bothkennar could probably never have been justified by the actual level of industrial and academic support for soft clay research in the UK. However, the clock cannot be turned back and it is vital now to find some way of preserving this anomalous archive in such a way that future generations of researchers can reap the benefits of the work of the past decade.

David Muir Wood is professor of civil engineering at Bristol University. He is part of a group interested in the future of Bothkennar that met at BRE on 28 April.

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