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UK guidelines for baseline reports needed

Lack of consistency among geotechnical baseline reports (GBRs) is impacting on their potential benefits and UK guidelines are need to ensure the potential is realised.

Speaking at a joint British Geotechnical Association and British Tunnelling Society meeting last night, geotechnical consultant GCG partner Helen Scholes said that by setting out the expected ground conditions, GBRs help improve establishing whether actual ground conditions are unforeseen or not. “This allows for an efficient assessment of claims,” she said.

Currently GBRs are generally only used on tunnelling projects but OTB Engineering’s Darren Page, who also spoke at the event, said that GBRs could benefit other geotechnical projects too. Page is leading the Engineering Group of the Geological Society work on developing GBR guidelines and the report is expected to be published next year.

Questions from the audience suggested that there is strong support for GBR guidelines in the UK, however, there was concern that these client-led documents have too much involvement from commercial and legal advisers and not enough from geotechnical specialists. Attendees called for the guidelines to include the requirement for GBRs to include input from “competent persons”.


What is a GBR?

A geotechnical baseline report (GBR) is a document setting out what the expected ground conditions on a project will be and in effect creates a specification for the ground in the same way other elements of construction are specified. In the event of the project running into difficulties due to ground conditions, the GBR can be used to decide if the conditions are really unforeseen and therefore create potential for a claim or fall within the conditions expected at the site.

GBRs were first suggested in the 1970s and research body Ciria produced a report on Ground Reference Conditions in 1978. Nonetheless, GBRs have only been adopted by the UK tunnelling sector in the last 10 years and were not mentioned in contract specifications until 2003.

Readers' comments (1)

  • The attempt to use GBRs is commendable and certainly they should not be written to win some future contractual argument. Nevertheless there is a general problem with GBRs in that if they use summary terminology as in a Q or RMR value or even a joint spacing plus UCS range then they probably oversimplify the situation. Unfortunately classifications and standardised description terms 'dumb down' geology so, whilst they might be understood by all, they do not allow critical conditions to be defined. There is no simple answer to this but use of GBRs will probably be fine for 99% of projects (where they are not really needed) but when things become difficult they will be found to be flawed.

    Steve Hencher

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