Japanese underground research laboratory project and prediction of rock mass behavior around deep shafts and galleries using continuous and discontinuous models

日本の深地層の研究施設計画と連続体及び不連続体モデルを用いた坑道掘削時の周辺岩盤挙動の予測

佐藤 稔紀  ; 見掛 信一郎 ; 中間 茂雄 ; 瀬野 康弘; 森 孝之*; 岩野 圭太*; 郷家 光男*; 多田 浩幸*

Sato, Toshinori; Mikake, Shinichiro; Nakama, Shigeo; Seno, Yasuhiro; Mori, Takayuki*; Iwano, Keita*; Goke, Mitsuo*; Tada, Hiroyuki*

日本の二つの深地層の研究施設のうち,瑞浪超深地層研究所の建設や研究の現状を紹介するとともに、MBCモデルやクラックテンソルモデルなどの連続体モデルと、クラックプロパゲーションコードを用いた不連続体モデルによる坑道掘削解析の結果を紹介する。

Two one-thousand meter deep shafts and research galleries at several levels will be excavated in granite for the Mizunami Underground Research Laboratory (MIU) project. Research on the deep geological environment in this project will provide the basis for Research and Development on geological disposal of high-level radioactive waste. The site of MIU project is located in Mizunami, Gifu, in the central part of the main island of Japan. By July 2003, entrances to the shafts were constructed, and excavation of lower part of shaft entrance was started in March 2004. Current status (September 2005) of construction is excavation of the shafts to a depth of 150 m has been done. Mechanical investigations including hydraulic fracturing test and laboratory tests on core samples were performed, and numerical analysis using continuous model and discontinuous model; MBC (Micro-mechanics based continuum model), Crack tensor model and FRACOD (fracture propagation code), were also performed to predict mechanical stability of openings and support systems, and rock mass behavior around openings. In this analysis EDZ (Excavation Damaged Zone) due to blasting and excavation step were considered in same cases. This paper describes the current status of Mizunami Underground Research Laboratory for crystalline rock and the results of prediction for rock mass behavior around the deep underground openings using some analytical methods. Measurements during shaft sinking and future plan of investigations in the URL are also describes in this paper.