ABSTRACT
The use of Geotechnical Baseline Report (GBR) as a risk allocation tool for tunnel and cavern projects is being adopted around the world. Whilst the overall benefits of using a GBR have been well publicised, there are various implementation issues related to the geological model, the details of physical and behavioural baselines, including their selection, definition, measurement and verification, and competency of the project team. In addition, whether a differing ground condition is foreseeable and how the entitlement for relief is determined need to be compatible with the contents of the GBR and the form of contract to realise the intended benefits. This paper provides a critical analysis of the issues related to GBR in the context of large scale, Design and Build, tunnel and cavern projects. Examples of physical and behavioural baselines and geohazards will be discussed based on the project experiences of the authors in Australia and overseas. The approaches of the FIDIC Emerald Book and the ASCE Gold Book, and their implications on the contracting parties will also be described. The impacts of these GBR related issues on design and construction are very significant, to the extent of dictating the project schedule and cost, which in turn influencing the success of the project. The final part of the paper attempts to summarise lessons learned from the discussions and some recommended practices.
