A call for detailed rock slope guidance
Adrian Koe & Thomas Clifford, Atkins, suggest guidance for rock netting is not keeping pace with technology and new best practice developments. They suggest this should be a future priority area for CIRIA research.
Rock Engineering technology and best practice has progressed significantly in the last 20 years. Data capture using remote survey techniques enables discontinuity orientations and roughness to be captured in areas difficult to access. Software development has progressed to a stage where numerous model scenarios can be run relatively quickly and complex numerical 3D analysis is routinely undertaken for the larger projects.
Remedial technology has also developed significantly, with many new rockfall barrier and netting products being available within the last 15 years.
However, guidance, is not keeping pace with these developments. The rock netting guide should be a welcome addition; however, this only focuses on one small area of rock engineering. Eurocode 7 was lacking in detail in relation to rock engineering. In the final report by the Evolution Group looking at Eurocode 7 (EG13) the opening paragraph stated that:
“
experience is showing that EN1997 is difficult, and in some circumstances impossible, to apply to rock engineering design and construction”
The Eurocodes will begin to undergo revision later this year, with a specific section on rock engineering. However, the work that is being recommended by EG13 to revise the standard, requires many of the basic principles to be established first and it seems unlikely that detailed guidance will be provided for some specific solutions, such as rock traps and barriers. It is not expected that any rockfall design or rock face maintenance guidance will be provided.
Within the UK, many of the rock engineering problems are within some low stress environments on infrastructure cuttings and much design work is still based on Rock Slope Engineering (Wyllie and Mah), many sections haven’t significantly changed since it was first published by Hoek and Bray in 1974. This useful text typically only provides guidance sufficient for preliminary design of remedial measures, and is lacking in the required detail to enable suitable planning, design, and maintenance of many rock remedial measures.
Without specific guidance there is a risk that mistakes in the application, design, operation and maintenance of rock slopes and rockfall protection systems, will result in remedial measures that are unfit for purpose.
Unfortunately, examples of bad practice are common within the UK as is shown in the photograph.
Should this be the one of the areas where CIRIA should focus research?
Rockfall barrier located behind residential gardens in Worcestershire.