Horonobe Underground Research Laboratory Project; Synthesis of Phase II (Construction Phase) investigations to a depth of 350m

Sato, Toshinori; Sasamoto, Hiroshi; Ishii, Eiichi; Matsuoka, Toshiyuki; Hayano, Akira; Miyakawa, Kazuya; Fujita, Tomoo*; Tanai, Kenji; Nakayama, Masashi; Takeda, Masaki; et al.

JAEA-Research 2016-025, 313 Pages, 2017/03

JAEA-Research-2016-025.pdf:45.1MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) to enhance the reliability of relevant disposal technologies through investigations of the deep geological environment within the host sedimentary formations at Horonobe, northern Hokkaido. This report summarizes the results of the Phase II investigations carried out from April 2005 to June 2014 to a depth of 350m. Integration of work from different disciplines into a "geosynthesis" ensures that the Phase II goals have been successfully achieved and identifies key issues that need to made to be addressed in the Phase II investigations Efforts are made to summarize as many lessons learnt from the Phase II investigations and other technical achievements as possible to form a "knowledge base" that will reinforce the technical basis for both implementation and the formulation of safety regulations.

Basic properties of the concrete using the low alkaline cement (HFSC) developed by JAEA

Seno, Yasuhiro*; Nakayama, Masashi; Sugita, Yutaka; Tanai, Kenji; Fujita, Tomoo

JAEA-Data/Code 2016-011, 164 Pages, 2016/11

JAEA-Data-Code-2016-011.pdf:8.45MB
JAEA-Data-Code-2016-011-appendix(CD-ROM).zip:0.1MB

The cementitious materials are used as candidate materials for the tunnel support of the deep geological repository of high-level radioactive wastes (HLW).Generally the pH of leachate from concrete mixed Ordinary Portland Cement (OPC) shows a range of 12 to 13. The barrier function of bentonite used as a buffer material and that of host rock might be damaged by the high alkaline leachate from cementitious materials. Therefore, low alkalinity that does not damage each barrier function is necessary for cementitious materials used for the tunnel support system of the HLW geological repository. JAEA has developed a low alkaline cement named as HFSC (Highly Fly-ash contained Silicafume Cement) which the pH of the cement leachate could lower approximately 11. We have confirmed the applicability of HFSC for the tunnel support materials, by using experimentally as the shotcreting materials to the part of gallery wall at 140m, 250m and 350m depth in Horonobe Underground Research Laboratory. And moreover, HFSC has been used as the cast-in-place concrete for the shaft lining concrete at the depth of 374m-380m. This Data/Code summarized the past HFSC mix proportion test results about the fresh concrete properties and hardened concrete properties, in order to offer the information as a reference for selecting the mix proportion of HFSC concrete adopted to the disposal galleries et al. in the future.

Long-term immersion experiments of low alkaline cementitious materials

Seno, Yasuhiro*; Noguchi, Akira*; Nakayama, Masashi; Sugita, Yutaka; Suto, Shunkichi; Tanai, Kenji; Fujita, Tomoo; Sato, Haruo*

JAEA-Technology 2016-011, 20 Pages, 2016/07

JAEA-Technology-2016-011.pdf:7.56MB

Cementitious materials are expected to be used for the construction of an underground repository for the geological disposal of radioactive wastes. Ordinary Portland Cement(OPC) would conventionally be used in the fields of civil engineering and architecture, however, OPC has the potential to generate a highly alkaline plume (pH12.5), which will likely degrade the performance of other barriers in the repository such as the bentonite buffer and/or host rock. Low alkaline cementitious materials are therefore being developed that will mitigate the generation of a highly alkaline plume. JAEA has developed a High-volume Fly ash Silica fume Cement (HFSC) as a candidate low alkaline cementitious material. The workability of the HFSC shotcrete was confirmed by conducting In-situ full scale construction tests in the Horonobe underground research laboratory. This report summarizes the results of immersion tests to assess the long-term pH behavior of hardened HFSC cement pastes made with mix designs that are expected to be able to be used in the construction of an underground repository in Japan.

Excavation damaged zone inferred by geophysical surveys on drift floor of Horonobe URL

Tokiwa, Tetsuya*; Aoyagi, Kazuhei; Fujita, Tomoo

Rock Mechanics and Rock Engineering; From the Past to the Future (EUROCK 2016), p.901 - 906, 2016/07

A Study of excavation damaged zone induced around the modeled disposal pit in Horonobe Underground Research Center

Aoyagi, Kazuhei; Ishii, Eiichi; Nakayama, Masashi; Fujita, Tomoo

Nihon Zairyo Gakkai Dai-65-Ki Tsujo Sokai, Gakujutsu Koenkai Rombunshu (USB Flash Drive), p.19 - 20, 2016/05

no abstracts in English

Measurement of the deformation behavior of the rock mass in the 350 m gallery in the Horonobe Underground Research Laboratory

Sakurai, Akitaka; Aoyagi, Kazuhei; Fujita, Tomoo; Motoshima, Takayuki*

JAEA-Data/Code 2015-023, 46 Pages, 2016/02

JAEA-Data-Code-2015-023.pdf:48.03MB
JAEA-Data-Code-2015-023-appendix(CD-ROM).zip:48.51MB

In a high level radioactive waste (HLW) disposal project, it is necessary to investigate the long-term behavior of thermos-hydro-mechanical-chemical of the rock mass around the engineered barrier system of the HLW waste for the safety assessment of the disposal system. In addition, long-term stability of the rock mass around the galleries are required for the disposal facility. Considering these backgrounds, the authors measure the deformation behavior of the vertical pit drilled on the floor of the 350 m gallery in the Horonobe Underground Research Laboratory. In situ measurements of the deformation of the pit and rock mass around the pit was conducted to apply to the assessment of the long-term deformation behavior. The authors describe the drilling of the vertical pit, geological observation, specification of the measurement instrument, measurement method, and result of the measurement in this report.

Evaluation of EDZ (Excavated Damage Zone) by multi-optical measurement probe in Horonobe Underground Research Center

Hata, Koji*; Niunoya, Sumio*; Aoyagi, Kazuhei; Fujita, Tomoo

Dai-44-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.319 - 324, 2016/01

Long-term monitoring and EDZ (Excavated Damage Zone) evaluation is carried out by this multi-optical measurement probe in the depth of 350m vertical shaft of Horonobe Underground Research Center project of the Japan Atomic Energy Agency. We have developed a multi-optical measurement probe incorporating an optical AE sensor, an optical water pressure sensor and an optical temperature sensor. Result of the measurement of AE, water pressure and temperature, it was made clear the influence of the shaft excavation. And from the source location analysis, it was found EDZ was less than 1.5m from shaft wall.

Estimation of initial stress based on the convergence measurement result during tunnel excavation

Kamemura, Katsumi*; Fujita, Tomoo; Aoyagi, Kazuhei; Nago, Makito*; Shirase, Mitsuyasu*; Sugawara, Kentaro*

Dai-44-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.109 - 114, 2016/01

How to estimate the initial stress state as well as a mechanical characteristic of rock mass is important in the design of deep underground structures. Some stress measurement methods using borehole, which methodology and evaluation method have been discussed in detail, are carried out if necessary. However, obtained results are often varying widely, so the evaluation of initial stress is difficult. Here, the initial stress state corresponding to the rock mass behavior of about 120m200m area is evaluated using the convergence measurement results during tunnel excavation in 350m depth. Analysed result corresponded to that of other method, so the validity of the proposed method was shown.

Study on the applicability of the fiber-optic crack detection sensor as a safety technology (Joint research)

Hiraiwa, Kenichi*; Hirai, Kazuhide*; Sano, Tadashi*; Osawa, Hideaki; Sato, Toshinori; Aoyagi, Yoshiaki; Fujita, Tomoo; Aoyagi, Kazuhei; Inagaki, Daisuke*

JAEA-Technology 2015-033, 50 Pages, 2015/11

JAEA-Technology-2015-033.pdf:12.6MB

Japan Atomic Energy Agency (hereinafter referred to as JAEA) has been conducted a geoscientific research and development project at the Mizunami Underground Research Laboratory and the Horonobe Underground Research Laboratory in order to construct scientific and technological basis for geological disposal. As a collaborative research between JAEA and Tokyo Sokki Kenkyujo Co., Ltd. (hereinafter referred to as TML), we focused on the fiber-optic crack detection sensor developed by TML as a method to detect cracks in the support system that may affect the stability of rock cavern during the operation. To verify long-term safety performance of the sensor for decades, "Evaluation test of long-term durability of fiber-optic crack detection sensor and the support system" at the Mizunami Underground Research Laboratory and "Performance evaluation test of fiber-optic crack detection sensor for in-situ crack detection" at the Horonobe Underground Laboratory Research Laboratory were conducted. As the result, we understand that fiber-optic crack detection sensor is applicable measurement method to promptly detect the cracks in the support system.

Evaluation of deep shaft excavation with computerized construction; Horonobe Underground Research Laboratory, Underground Research Facilities Project (2nd Period)

Fujita, Tomoo; Aoyagi, Kazuhei; Nago, Makito*

Tonneru To Chika, 46(7), p.481 - 489, 2015/07

The Japan Atomic Energy Agency (a National Research and Development Agency) is constructing shafts and research tunnels in Horonobe-cho, Teshio-gun, Hokkaido as part of the Horonobe Underground Research Project. This report summarizes investigations into computerized construction while excavating the shaft for the Horonobe Underground Research Centre. Cracking in the lining concrete occurred due to the development of rock spalling near the wall surface while excavating the ventilation shaft. To that end, we created a flowchart to select kinds of shaft supports for use in subsequent works that took steps appropriate for the bedrock collapse phenomenon during excavating, countermeasures for this and extent of spalling. In addition, this report contains information on pre-grouting works on the fault zone and its results which were conducted as a measure against groundwater inflow which can be a problem during excavating works and also the results of these works.