Countermeasures planned for reducing water inflow into deep shafts at the Mizunami Underground Research Laboratory

Kuji, Masayoshi; Sato, Toshinori  ; Mikake, Shinichiro ; Hara, Masato; Minamide, Masashi; Sugihara, Kozo

The Mizunami Underground Research Laboratory (MIU) is being constructed. The MIU consists of two 1,000 m-deep shafts with several research galleries. The goals of MIU project are to establish techniques for investigation, analysis and assessment of deep geological environment, and to develop a range of engineering expertise for application to deep underground crystalline rocks, such as Granite. The diameter of the Main and the Ventilation shafts are 6.5 m and 4.5 m respectively. The Middle stage at about 500 m depth, and the Main stage at about 1,000 m depth will be the main locations for scientific investigations. Current depths of both shafts are 200 m, in August 2007.During the construction, the water inflow into the shafts is increasing and disturbing the project progress. For reducing the water inflow, post-excavation grouting was planned. A test of post-excavation grouting was undertaken and the applicability of several techniques was evaluated.