An ultrasonic tool for examining the excavation damaged zone around radioactive waste repositories - The OMNIBUS project

This paper describes current results from the OMNIBUS project, a study funded by the EC as part of the fifth framework EURATOM programme. The objective of the project is to develop ultrasonic monitoring tools and associated technologies for investigating the rock barrier in both potential and operational underground nuclear waste repositories. A complete data acquisition tool has been developed and has been successfully tested during an in situ experiment aimed at studying an argillaceous rock layer. The tool includes an integrated hardware and software package specifically designed for monitoring an argillaceous rock mass. Numerical models are being used to provide a sensitivity analysis of ultrasonic wave propagation to variations in stress, crack population and fluid content. Through this approach we aim to improve our understanding of how ultrasonic data can be interpreted in terms of useful engineering rock-mass properties. Data from laboratory and in situ experiments will be used to develop and test the strategy. (authors)