Horonobe URL project; Experience on borehole investigations in surface-based investigation phase

Matsui, Hiroya 

JAEA(Japan Atomic Energy Agency) has been conducting the project which is combined with construction of URL(Underground Research Laboratory) on Neocene sedimentary rock in Horonobe-cho, Hokkaido, Japan. This project, conjugate with the MIU project on crystalline rock in Mizunami-shi, Gifu-prefecture, Japan, was started FY1999/2000. The total duration of the project is about twenty years. The project consist of the following three phases; Surface-based investigation phase Construction phase Operation phase. This report summarizes the experience for deep borehole investigation in surface based investigation phase, which is most important investigation in the phase. The all deep borehole investigations had been planed and carried out in taking account of not only technical consideration but also practical and social aspects. Specifically, the report describes the important suggestions derived from the work of the deep borehole investigations.