Status of grouting to reduce groundwater inflow into deep shafts and galleries in the Mizunami Underground Research Laboratory, Japan

瑞浪超深地層研究所における湧水抑制対策としてのグラウトの現状

佐藤 稔紀  ; 見掛 信一郎 ; 小林 伸司*; 辻 正邦*

Sato, Toshinori; Mikake, Shinichiro; Kobayashi, Shinji*; Tsuji, Masakuni*

日本原子力研究開発機構では、高レベル放射性廃棄物地層処分技術に関する研究開発を実施しており、その一環として超深地層研究所計画を実施している。この計画の中で、施工対策技術として湧水抑制対策技術に関する研究を実施している。瑞浪超深地層研究所の立坑や水平坑道においてグラウトを実施し、普通セメントで2ルジオン、超微粒子セメントで0.2ルジオン、溶液型シリカでは0.29ルジオンという透水性を達成することができた。

Japan Atomic Energy Agency is operating Mizunami Underground Research Laboratory project focusing on crystalline rock. Grouting for reducing water inflow is an essential countermeasure technology utilized during construction of underground facilities. Pre-excavation grouting and post-excavation grouting using Ordinary Portland cement, super-fine Portland cement and liquid-type colloidal silica were performed to investigate their performance as countermeasures for reducing groundwater inflow at many locations in the shafts and galleries in the laboratory. The results show that pre-excavation grouting successfully attained the target hydraulic conductivity of 2 Lu for Ordinary Portland cement and 0.2 Lu for super-fine Portland cement using criteria of Lugeon value and changing W/C. Liquid-type colloidal silica was able to drastically lower the hydraulic conductivity of 0.29 Lu and seemed to be stable for water pressures of at least 5 MPa and to be important material used in deep underground.