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Journal Articles

Initial stress measurement by hydraulic fracturing method in diatomaceous mudstone in the Horonobe Underground Research Laboratory

Kondo, Keiji; Tsusaka, Kimikazu; Inagaki, Daisuke; Sugita, Yutaka; Kato, Harumi*; Niunoya, Sumio*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.583 - 588, 2013/01

no abstracts in English

Journal Articles

Simultaneous measurements of a single fracture surface morphology and aperture distribution by an optical method

Sato, Hisashi; Sawada, Atsushi

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.501 - 506, 2013/01

The authors have developed the fracture surface geometry measurement method applied by the optical measurement system of a transparent fracture replica specimen, under the same conditions as hydraulic test. Fracture surface geometry measured by the optical method shows closer shape by an alternative method, laser displacement meter. This method require to be improved, because noisy error at local points and at the edge of the specimen was found. The fracture surface geometry data is useful to correlate transmissivity estimated from aperture data based on local cubic law. The transmissivity is successfully correlated by taking account for effects of fracture slope onto transmissivity and length along flow paths.

Journal Articles

Development of grouting technologies for geological disposal of high level waste in Japan, 7; Hydrological and chemical change of the groundwater in a pre-grouted crystalline rock after earthquakes

Matsui, Hiroya; Mizuno, Takashi; Sasamoto, Hiroshi; Sato, Toshinori

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.365 - 370, 2013/01

Japan Atomic Energy Agency has been conducted a contract study with METI (Ministry of Economy, Trade and Industry) called "The project for Grouting Technology Development" since 2008. As a part of the study, the monitoring of groundwater chemistry in a pre-grouted area has been carried out for four years after pre-grouting in Mizunami URL. Measured groundwater pressures were temporarily changed by the earthquakes with more than three of seismic intensity and it was recovered within about one year. Meanwhile, the change of the chemical compositions in groundwater by the earthquakes were not detected and it show a injected grout material was not damaged significantly.

Journal Articles

Study on dynamic behavior of a shaft excavated through faulted crystalline rock mass

Hashizume, Shigeru; Matsui, Hiroya; Horiuchi, Yasuharu; Hata, Koji*; Akiyoshi, Kenji*; Sato, Shin*; Shibata, Chihoko*; Niunoya, Sumio*; Noda, Masaru*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.121 - 126, 2013/01

The "Mizunami Underground Research Laboratory" has been studying and developing engineering technology for deep underground applications. These applications are multifaceted and are categorized as development of design and construction planning technology, development construction technology, development countermeasure technology, and development of technology for construction and operation security. In this report, the dynamic stability of shaft and surrounding rock mass has been studied with respect to rock mass displacement and stress, the effect of using a concrete liner and excavating through faulted crystalline rock.

Journal Articles

Numerical simulations and analysis for the $"A$sp$"o$ pillar stability experiment, 1; Continuum based approaches using finite element method and comparison with other analysis model

Chijimatsu, Masakazu*; Koyama, Tomofumi*; Shimizu, Hiroyuki*; Nakama, Shigeo; Fujita, Tomo

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.437 - 442, 2013/01

DECOVALEX-2011 is an international cooperation project for enhancing the numerical models of radioactive waste repositories. In Task B of DECOVALEX-2011 project, the failure mechanism during excavation, heating and destressing processes observed in the $"A$sp$"o$ pillar stability experiment (APSE), which carried out at the $"A$sp$"o$ Hard Rock Laboratory by the Swedish Nuclear Fuel and Waste Management Company (SKB), were simulated using Finite Element Method. When the calibrated parameters were used, simulation results agree qualitatively well with the experimental results. Therefore, it can be said that the spalling phenomenon is expressible even by the application with the continuum model by the use of the suitable parameters.

Journal Articles

Numerical simulations and analysis for the $"A$SP$"O$ pillar stability experiment, 2; Discontinuum based approaches using distinct element method

Shimizu, Hiroyuki*; Koyama, Tomofumi*; Chijimatsu, Masakazu*; Fujita, Tomo; Nakama, Shigeo

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.443 - 448, 2013/01

DECOVALEX-2011 is an international cooperation project for enhancing the numerical models of radioactive waste repositories. In Task B of DECOVALEX-2011 project, the failure mechanism during excavation, heating and destressing processes observed in the $"A$sp$"o$ pillar stability experiment (APSE), which carried out at the $"A$sp$"o$ Hard Rock Laboratory by the Swedish Nuclear Fuel and Waste Management Company (SKB), were simulated using two dimensional Distinct Element Method. As a result, it is found that the simulated crack generation and propagation during the destressing process by 2D-DEM agree qualitatively well with the observation at site.

Journal Articles

Strength and impermeability recovery of siliceous mudstone from complete failure

Sugita, Yutaka; Sanada, Masanori; Fujita, Tomo; Hashiba, Kimihiro*; Fukui, Katsunori*; Okubo, Seisuke*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.207 - 212, 2013/01

Radionuclide migration can be undesirably increased by weakening the mechanical properties of a rock mass in the excavated disturbed zone (EDZ) around the tunnels of a geolical disposal facility for high level radioactive waste. Laboratory testing of loading stress and loading time on failed siliceous mudstone specimens has identified the potential for the long-term recovery of the strength and impermeability of the rock mass in the EDZ.

Journal Articles

Development of rock segment for reduction of amount of cement use

Tada, Hiroyuki*; Kumasaka, Hiroo*; Saito, Akira*; Nakaya, Atsushi*; Ishii, Takashi*; Sanada, Masanori; Noguchi, Akira*; Kishi, Hirokazu*; Nakama, Shigeo; Fujita, Tomo

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.133 - 138, 2013/01

The authors have been developing methods for constructing tunnels using the minimum quantities of cement-type support materials in high-level radioactive waste disposal facilities and advancing research and development about the technical formation of rock segment using low alkaline mortar. In this study, the mechanical characteristic values concerning the rock segment and backfill materials were examined. The stability analysis of tunnel supported by the rock segment and backfilling with gravel were performed. Technical formation and effectiveness of the alternative supports planned for further reduction in cement influence was confirmed from a study result above-mentioned.

Journal Articles

Development of grouting technologies for geological disposal of high level waste in Japan, 2; Selection of grout materials

Kawaguchi, Masanao; Kishi, Hirokazu*; Fujita, Tomo; Kishida, Kiyoshi*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.337 - 342, 2013/01

For the selection of grout material for the construction of underground facilities for the geological disposal of High Level Waste, the criteria that is set by reference to IMA-project(which was a project of the grout material relating to the R20 program was conducted by POSIVA of Finland), has been used up to FY 2010. However, if the criteria of penetrability are fulfilled, the penetrability of the material for the candidate rock fracture is not ensured. Moreover, from the results of laboratory grout penetration test which has been carried out at FY 2010, it was appeared that the penetrability has been scarified in order to satisfy the strength and breeding characteristics. In this report, strength and bleeding properties are classified as reference properties, not as principal properties. Instead of that, new criteria of penetrability defined based on geological features at the site are proposed. Also the determination procedure of designed hydraulic fracture aperture which is one of above newly proposed criteria will be proposed.

Journal Articles

Study on connectivity of water-conducting features from the spatial changes of transmissivity based on the hydraulic packer testing data

Takeuchi, Shinji*; Sawada, Atsushi; Takeuchi, Ryuji; Daimaru, Shuji*; Toya, Naruhisa*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.143 - 148, 2013/01

Transformation of transmissivity from derivative of pressure traisnet data obtained from hydraulic packer testing has applied to the testing data from fractured rock of Mizunami site Japan and Onkalo site Finland. The results show hydrogeological conceptual model for the tested area such as connectivity and continuity of the water-conducting features could be established by the proposed methodology. This method would provide useful information to the hydrogeologial and transport modeling and simulation.

Journal Articles

Planning of in-situ experiment for understanding of gas migration behaviour in sedimentary rock, 1; Setting of gas injection procedure

Tanai, Kenji; Fujita, Tomo; Noda, Masaru*; Yamamoto, Shuichi*; Shimura, Tomoyuki*; Sato, Shin*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.167 - 172, 2013/01

Japan Atomic Energy Agency has been planning in-situ gas migration test in Horonobe URL, Hokkaido. This paper discusses the optimum gas injection procedure for the test to understand gas migration behaviour in surrounded rock. The stepwise constant gas injection was selected, taking into account domestic and overseas gas related research results. Hydro-mechanical-gas coupling analysis which is able to consider the dissolved methane in Horonobe groundwater was applied to evaluate the gas behaviour. The results have indicated no significant mechanical damages to the rock and have supported the sppropriateness of selected gas injection procedure for the test.

Journal Articles

Planning of in-situ experiment for understanding of gas migration behaviour in sedimentary rock, 2; Affects of dissolved methane to the gas migration in bedrock

Tanai, Kenji; Fujita, Tomo; Sato, Shin*; Noda, Masaru*; Yamamoto, Shuichi*; Shimura, Tomoyuki*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.173 - 178, 2013/01

Japan Atomic Energy Agency has been planning ${it in-situ}$ gas migration test in Horonobe URL, Hokkaido. It is expected that dissolved methane in Horonobe groundwater might have an effect on gas migration behaviour in bedrock. A series of two-phase multi-component analyses by use of GETFLOWS were conducted to understand the influence of dissolved methane. The increase of total gas pressure has been shown due to the existence of dissolved methane. The results also indicated that the injected nitrogen gas volume was influenced by dissolved methane.

Journal Articles

Influence of rock spalling on concrete lining in shaft sinking at the Horonobe Underground Research Laboratory

Tsusaka, Kimikazu; Inagaki, Daisuke; Nago, Makito*; Koike, Masashi*; Matsubara, Makoto*; Sugawara, Kentaro*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.911 - 916, 2013/01

A repository for high-level radioactive waste in deep underground consists of several underground structures such as access and disposal drifts and shafts. In deep geological disposal project, a shaft is the first underground structure to be constructed and the last one to be backfilled. Therefore, the stability of shaft is one of key factors to steadily manage the project in the construction and operation phases. In this paper, the authors discuss influence of rock spalling on concrete lining in shaft sinking. Japan Atomic Energy Agency has been constructing three shafts (one is for ventilation and the others are for access use) up to a depth of 500 m in the Horonobe Underground Research Laboratory. During the construction of the Ventilation Shaft (4.5 m in diameter) below a depth of 250 m, rock spalling occurred at several depths and an open crack has developed in a concrete lining installed just above rock spalling. The authors have measured geometry of shaft wall by using three-dimensional laser scanner. They also conducted numerical analysis in order to calculate change in stress distribution and deformation induced by rock spalling in a concrete lining and the surrounding rock. As a result, it was clarified that rock spalling induced tensile stress in the vertical direction in a concrete lining. Especially, the tensile stress in a concrete lining was likely to exceed tensile strength of a concrete lining in the case that it developed more than 100 cm in depth.

Journal Articles

Repetition of spectral analysis on rock permeability applied to seven years record of pore-pressure response to atmospheric loading at the Horonobe URL in Japan

Miyakawa, Kazuya; Nohara, Tsuyoshi; Tokiwa, Tetsuya; Yamazaki, Masanori*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.1027 - 1032, 2013/01

Understanding of geological environment has been required for radioactive waste disposal, and the permeability of rock mass is one of the most important characteristics of disposal system. It is reported that rock permeability can be estimated by the spectral analysis of the records of pore pressure and atmospheric pressure. JAEA began the Horonobe Underground Research Laboratory (Horonobe URL) Project as part of efforts to enhance the reliability of technologies used during the geological disposal of HLW in Japan. In this study, a spectral analysis of vertical permeability in sedimentary formation around the underground facility has been carried out with seven years records of pore pressure and atmospheric pressure in the Horonobe URL. This study revealed that the excavation of URL has influenced groundwater layers around the URL, and has reduced the vertical hydraulic permeability in the layers. At a point approximately 130 m distant from the URL, it was found that hydraulic diffusivity has decreased by approximately 15 - 70% in five years since the excavation started. This study indicated that permeability change during the excavation of URL could be monitored via pore and atmospheric pressure records.

Journal Articles

Occurrence of high-permeability fracture estimated by grouting in Horonobe URL of Japan

Tokiwa, Tetsuya; Sawada, Sumiyuki; Ochiai, Shoji; Miyakawa, Kazuya

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.1021 - 1025, 2013/01

In the Horonobe area of Japan, underground facilities have been excavated in soft sedimentary rocks in order to enhance the reliability of relevant technologies for geological disposal of high-level radioactive waste in Japan. Pre-excavation grouting was carried out at 250 to 380 m depth at the location of the planned Ventilation Shaft. After the grouting, the shaft was excavated from 250 to 350 m depth, and fracture mapping was carried out to understand the characteristics of water conductive fractures by focusing on the occurrence of injected grout. Fractures consist mainly of shear fractures, and extension fractures and faults are observed in the shaft. The faults are associated with fault rocks and high continuity. Grout was mainly observed in fractures located on the branching part from faults rather than the fault itself, and therefore high-permeability fractures are not the fault itself (fault core) but fractures located on the branching part in the damage zone of the fault.

Journal Articles

Geomechanical assessment of excavation damaged zone in the Horonobe Underground Research Laboratory, Japan

Aoyagi, Kazuhei; Tsusaka, Kimikazu; Tokiwa, Tetsuya; Kondo, Keiji; Inagaki, Daisuke

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.905 - 910, 2013/01

In a high-level radioactive waste (HLW) disposal project, quantitative evaluation of the extent of excavation damaged zone (EDZ), which is estimated to cause the mechanical, hydrological and geochemical effect to the rock. In Horonobe URL, P-wave tomography survey and rock core observation in the tomography area were conducted at the depth of 250 m to evaluate EDZ. In addition to these in-situ measurement and observation, the authors conducted numerical analysis to identify damaged zone. As a result of P-wave tomography, remarkable low velocity layer was extended about 0.6 m from the drift wall. From the result of rock core observation, the region which has several EDZ fractures developed to 0.3 m from the gallery wall. Furthermore, the numerical analysis showed that the failure zone was extended about 0.2 m from the drift wall. From these results, the authors concluded that the extension of remarkable low velocity layer matched with the extension of the region which has several EDZ fractures.

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