Confirmation of the applicability of low alkaline cement-based material in the Horonobe Underground Research Laboratory

Nakayama, Masashi; Niunoya, Sumio*; Minamide, Masashi*

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 23(1), p.25 - 30, 2016/06

https://doi.org/10.3327/jnuce.23.1_25

In Japan, any high-level radioactive waste repository is to be constructed at over 300m depth below surface. Tunnel support is used for safety during the construction and operation, and shotcrete and concrete lining are used as the tunnel support. Concrete is a composite material comprised of aggregate, cement and various additives. Low alkaline cement has been developed for the long term stability of the barrier systems whose performance could be negatively affected by highly alkaline conditions arising due to cement used in a repository. Japan Atomic Energy Agency (JAEA) has developed a low alkaline cement, named as HFSC (Highly fly-ash contained silicafume cement), containing over 60wt% of silica-fume (SF) and coal ash (FA). JAEA is presently constructing an underground research laboratory (URL) at Horonobe for research and development in the geosciences and repository engineering technology. HFSC was used experimentally as the shotcrete material in construction of part of the 350m deep gallery in Horonobe URL in 2013. The objective of this experiment was to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on. HFSC used in this experiment is composed of 40wt% OPC (Ordinary Portland Cement), 20wt% SF, and 40wt% FA. This composition was determined based on mechanical testing of various mixes of the above components. Because of the low OPC content, the strength of HFSC tends to be lower than that of OPC in normal concrete. The total length of tunnel constructed using HFSC shotcrete is about 112m at 350m deep drift. The workability of HFSC shotcrete was confirmed by this experimental construction. In this report, we present detailed results of the in-situ construction test.

Gas control measures taken during deep shaft excavation

Nago, Makito*; Hagihara, Takeshi*; Minamide, Masashi*; Motoshima, Takayuki*; Jin, Kazumi; Kudo, Hajime; Sugita, Yutaka; Miura, Yoichi*

Dai-49-Kai Zenkoku Kensetsugyo Rodo Saigai Boshi Taikai Kenkyu Rombunshu (CD-ROM), p.77 - 80, 2012/10

This paper presents measures against gas emission during deep shaft excavation in the Horonobe Underground Research Laboratory Project (Horonobe URL Project). The gas control measures taken in the Horonobe URL Project include the following: (1) determination of the amount of methane contained in surrounding strata and groundwater, and gas concentration based on preliminary investigations, (2) determination of the specifications of fans, dust collectors, and ducts through ventilation network analysis (simulation), (3) reduction of methane gas emission through the use of waterproofing grout, (4) prohibition on the use of internal-combustion engine and the adoption of explosion-proof equipment, (5) development of methane gas control system, and (6) monitoring of methane gas emission. (3) to (6) described above are performed daily in the safety management activities and described in detail in this paper. The ventilation and eastern access shafts have currently reached a depth of 290 m and 250 m, respectively. The emission of methane gas has been observed to rise 0.3 % to 1.3 % in the fault zone, and it is controlled appropriately according to the gas control measures described above. As the measure to reduce the methane gas concentration, monitoring is confirmed to be effective.

Countermeasures planned for reducing water inflow into deep shafts at the Mizunami Underground Research Laboratory (Research for post-excavation grouting)

Kuji, Masayoshi*; Matsui, Hiroya; Hara, Masato; Minamide, Masashi*; Mikake, Shinichiro; Takeuchi, Shinji; Sato, Toshinori*; Asai, Hideaki

JAEA-Research 2008-095, 54 Pages, 2009/01

JAEA-Research-2008-095.pdf:13.14MB

A large amount of water inflow is frequently generated during the excavation of an underground cavern, such as road and railway tunnels, underground electric facilities etc. The reduction of water inflow is sometimes quite important for the reduction of cost for the water treatment and pumping during the construction of an underground cavern. The Mizunami Underground Research Laboratory (MIU) is currently being constructed by Japan Atomic Energy Agency. During its excavation, a large amount of water inflow into the shafts has been increasing and affecting the project progress. Therefore, a field experiment of post-excavation grouting around the Ventilation Shaft in a sedimentary formation carried out to confirm the effect of existing grouting technology for sedimentary formations in MIU project. The result shows that the applied methods in this field experiment are effective to prevent water inflow. This report describes the summary of the field experiment and the knowledge obtained through the experiment.

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

Journal of Power and Energy Systems (Internet), 2(1), p.153 - 163, 2008/00

https://doi.org/10.1299/jpes.2.153

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.

Post-grouting test to reduce water inflow into deep shaft

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

Tonneru Kogaku Hokokushu (CD-ROM), 16, p.469 - 476, 2006/11

http://library.jsce.or.jp/jsce/open/00047/2006/16-0469.pdf

In the Mizunami Underground Research Laboratory (MIU), two 1,000m-deep shafts and several research galleries are being constructed. Water inflow into the shafts during shaft sinking is disturbing the project progress. As a countermeasure for this problem, post-grouting is being considered and post-grouting test has been undertaken in one of the shafts. This report gives an outline of the work plan and results of the post-grouting test.

Evaluation of the quantity of injected grouting material by post-excavation grouting tests conducted at different injection rounds at Mizunami Underground Research Laboratory

Kuji, Masayoshi; Hara, Masato; Minamide, Masashi; Mikake, Shinichiro; Sato, Toshinori; Ikeda, Koki

no journal, , 

no abstracts in English

Pre-grouting to reduce water inflow in the ventilation shaft into the Mizunami Underground Research Laboratory

Hara, Masato; Kinoshita, Harunobu; Ikeda, Koki; Yamamoto, Masaru; Yahagi, Ryoji*; Kikuchi, Shinji*; Kawano, Hiromichi*; Ushida, Kazuhito*; Nobuto, Jun*; Minamide, Masashi*

no journal, , 

At the Mizunami Underground Research Laboratory, inflow water control to inside the tunnel has become topic. Because of this, the pre-grouting at inside the tunnnel of depth 200m was executed. In this report, it is something which is reported concerning the result of the pre-grouting.

Analysis of shaft construction cyclic time at Horonobe Underground Research Laboratory Project

Kitagawa, Yoshito*; Yamazaki, Masanao; Hagihara, Takeshi*; Minamide, Masashi*; Sekiya, Yoshitomo

no journal, , 

no abstracts in English

In-situ experiment using low-alkaline cement shotcrete, 1; Mix design of composition of the shotcrete for the underground gallery support

Noguchi, Akira; Nakayama, Masashi; Kishi, Hirokazu; Kitagawa, Yoshito*; Minamide, Masashi*

no journal, , 

We are researching about the low alkaline cement applying to support of galleries for high-level radioactive waste repositories. In March, 2009, we performed a experiment of shotcrete with low alkaline cement whose proportion of the binder is 40% of ordinary portland cement, 20% of silicafume and the rest 40% of flyash. By selecting the proportion 30% water binder ratio and adding superplasticizer, the slump was 23 cm and compressive strength of the hardened concrete was 38.3 MPa. This proportion satisfied the standard of the support of the Horonobe Underground Research Laboratory whose compressive strength is more than 36 MPa and slump is around 21cm. The rebound ratio of the shotcrete was around 13%. This value is lower than that of ordinary portland cement. So, we can expect to get a better construction environment with this shotcerte. We decided to use this proportion in the in-situ experiment at the 140 m gallery in the Horonobe URL.

Investigating technique for understanding of pre-grouting area in sedimentary soft rocks

Sawada, Sumiyuki; Tokiwa, Tetsuya; Kumagai, Seiya; Minamide, Masashi*

no journal, , 

Underground facilities have been excavated in soft sedimentary rocks in the Horonobe area, Hokkaido, Japan. Spring water induced by excavation is a major issue, and therefore it is need to implement the spring water control by pre-grouting before the excavation for the efficient and safety excavation. The flow point needed to inject the grouting had been calculated by using borehole investigation data (e.g., core observations and Fluid Electric Conductivity Logging), and boring for pre-grouting was carried out. As a result, calculated flow points are identical with actual flow points. Therefore, it is quite likely to assess and predict the flow points by focusing on borehole investigation data.