The Japan Atomic Energy Agency (JAEA) has been developing advanced grouting technologies and grout materials to seal fractures in the host rock of an underground disposal facility (repository) for the geological disposal of high level waste (HLW) in Japan. As a part of the JAEA Grout Project (JGP), this paper describes the in-situ grout injection test program carried out in the fractured granite of the Grimsel Test Site (GTS) in Switzerland with the aim of improving grouting design, in order to reduce unnecessary grout penetration into rock mass and investigate appropriate site investigation techniques.

The in-situ grout injection test project at the GTS was carried out in three stages over three years. In the first stage, two parallel boreholes were drilled and surveyed by borehole TV (BTV). In the second stage, a third borehole was drilled, similarly surveyed and additional single borehole and cross-borehole hydraulic tests were conducted. The site investigation results were then used to determine the best configuration for the final stage of the grout injection test.

The staged approach proved to be a good way to determine the best location for the grout injection test and to determine the next stages by identifying and mitigating possible problems before they occurred.

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