Institute of Quarrying News
Nearly 50 members and guests gathered at the East Mendips Study Centre on 8 March to hear David Gibson, business development manager with BAM Ritchies, give a talk entitled 'Rock and Soil Slope Stabilization and Protection - Best Practice'.

David began by stating the requirements of the 1999 Regulations in terms of inspection, appraisal and assessment, and the need to provide adequate and economic solutions. He outlined the technology now available to assess possible failure mechanisms, such as stereo photography and laser scanning, and explained how dedicated software packages can determine the optimum forces at anchor points, as a function of the geotechnical parameters.

David explained the standard methods of stabilization, such as scaling and presplitting, before going on to describe active solutions such as rock bolting and ground anchors. One of the major issues associated with these techniques has been corrosion. However, modern manufacturing techniques and the use of new materials can now provide significantly longer life.

David then explained best practice in the use of soil nailing as an example of a passive solution. This is a similar method to anchoring but is installed with little or no tension. Its use has increased over the years, largely as a result of new guidance produced by CIRIA.

Access is a critical aspect of the operation and David described how advances in technology, such as boom mounted long reach excavators and remotely controlled rigs, have reduced the need for hand-held drilling. This, in turn, has led to a reduction in the incidence of HAYS. For some undertakings, BAM Ritchies have developed their own equipment to allow them todrill even on near vertical slopes.

David outlined the methods of soil retention using geotextiles and wire mesh, giving examples of how such methods had been employed on railway embankments and motorways, notably the M4 between Cardiff and Newport. The use of such methods in a rail cutting at Flax Bourton had reduced costs from £12million to £6million, compared with more conventional techniques, and had the added advantages of not requiring track possession while the work was being carried out, together with the fact that it could be seeded to produce a natural looking slope.

David concluded his tack by considering the issue of rock-fall protection. He said it was often more economic to catch rock rather than to try to support it, and he described the techniques now available which are capable of doing this. To illustrate the point, he showed a system being subjected to a test where a 16 tonne weight was dropped on to it from a height of 32m. In a quarry situation, this method could be employed to reduce berm widths or even eliminate them.

Throughout the talk, David illustrated his presentation with many examples from all over the world. A lively question and answer session concluded a very informative and thought-provoking evening. Kevin Sargant proposed the vote of thanks to a very accomplished and knowledgeable speaker.

Article courtesy of QM Institute - April 2010