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JAEA Reports

Studies on the design method of multi tunnels in geological disposal facility, 4

Hayashi, Katsuhiko; Kishi, Hirokazu; Kabayashi, Yasushi*; Takebe, Atsuji*; Fujiyama, Tetsuo*; Hiramoto, Masayuki*; Mizutani, Kazuhiko*; Morita, Atsushi*

JAEA-Research 2010-059, 92 Pages, 2011/03

JAEA-Research-2010-059.pdf:3.71MB

In this study, the first investigation is the order of the multi-tunnels excavation. The second is the strain-softening model for multi-tunnels which is based on test data at Horonobe site. As results of first investigation, we showed as 2 dimensional analyses that it was desirable to excavate the tunnel of the remote distance at first and excavate the tunnel between these tunnels next, and it is necessary for the examination that reflected a real plan, such as evacuation machine and actual multi tunnel layout. As the results of second investigation, we also showed the more reliable EDZ by using the strain-softening model that is based on test data at Horonobe site. Furthermore, we standardized the design method (draft) for the practical use by referring the past studies of multi tunnel design method.

JAEA Reports

A Study on the technology for reducing cement-type materials used for tunnel supports at high-level radioactive waste disposal sites (Joint research)

Hayashi, Katsuhiko; Noguchi, Akira; Kishi, Hirokazu; Kabayashi, Yasushi*; Nakama, Shigeo; Fujita, Tomoo; Naito, Morimasa; Tada, Hiroyuki*; Kumasaka, Hiroo*; Goke, Mitsuo*; et al.

JAEA-Research 2010-057, 101 Pages, 2011/03

JAEA-Research-2010-057.pdf:7.47MB

Cement-type materials that are used for supports or grouting at high-level radioactive waste disposal facilities leach into the groundwater and create a highly alkaline environment. Of concern in highly alkaline environments are the alteration of bentonite used as buffers or backfill materials, and of surrounding rock mass, and the increased uncertainty regarding the provision of performance of the disposal system over a long period of time. In this study, to reduce the quantity of cement-type materials that cause highly alkaline environments, technical feasibility of the support structure including the materials which considered the long-term performance of the HLW disposal system are discussed by using knowledge and technology accumulated in JAEA and Shimizu Construction. Moreover, based on the results, the problems remained in the application to the future HLW disposal institution are summarized.

JAEA Reports

Studies about strength recovery and generalized relaxation behavior of rock, 3

Hayashi, Katsuhiko; Kishi, Hirokazu; Kabayashi, Yasushi*; Takebe, Atsuji*; Okubo, Seisuke*

JAEA-Research 2009-058, 106 Pages, 2010/02

JAEA-Research-2009-058.pdf:18.82MB

In this study, experimental studies on the strength recovery, the generalized stress relaxation behavior and the tensile strength were conducted using samples obtained from the Wakkanai-formation shale. As the results, the strength recovery has time-dependent characteristics. It was founded that the generalized stress relaxation behavior depends on the draining conditions. Furthermore, regarding the tensile strength, complete stress-strain curve under uniaxial tensile strength conditions was gotten and it was found that there is small residual strength. The results of uniaxial tensile strength in this year are almost same as the minimum value of splitting tensile strength test results.

JAEA Reports

Studies on the design method of multi tunnels in geological disposal facility, 3

Hayashi, Katsuhiko; Kishi, Hirokazu; Kabayashi, Yasushi*; Takebe, Atsuji*; Fujiyama, Tetsuo*; Hiramoto, Masayuki*; Mizutani, Kazuhiko*; Morita, Atsushi*

JAEA-Research 2009-056, 86 Pages, 2010/02

JAEA-Research-2009-056.pdf:9.96MB

In this study, the effect of constitutive models such as strain softening of rock masses for EDZ, and the stress relief ratio used for multi tunnels analysis were conducted. As the result, it is necessary to confirm mechanical behavior of in situ rock and it is important to choose suitable constitutive models, and it is possible for all tunnels in multi tunnels model to have same stress relief ratio.

JAEA Reports

Study on applicability of low alkaline cement in Horonobe Underground Research Laboratory Project, 3 (Contract research)

Nakayama, Masashi; Kobayashi, Yasushi; Noguchi, Akira; Miura, Norihiko*; Noda, Masaru*; Iriya, Keishiro*; Hitomi, Takashi*

JAEA-Research 2009-036, 49 Pages, 2009/11

JAEA-Research-2009-036.pdf:20.34MB

In Horonobe Underground Research Laboratory (Horonobe URL) Project, construction practicality test with HFSC (Highly Fly-ash contained Silica-fume Cement) is planned in a part of the gallery. It is necessary to validate that HFSC has performance under the actual construction, before HFSC is placed in the gallery. The main tasks in 2008 are follows; (1) suggestion of mix design for liner concrete of shaft in Horonobe URL, (2) investigation of long term pH changes in order to use for modeling, and (3) an experiment for interaction between HFSC and ground water around Horonobe URL. (1) 4 types of mix proportion are designed for ordinary concrete and high strength concrete which contains polypropylene fiber or not. As early age strength, 5N/mm$$^{2}$$ is required because of concrete formwork. HFSC424 with low water binder ratio can fulfill this requirement in combination with super plasticizer. (2) pH and components of solid and liquid phase which were made in 2003, and stored in water were analyzed. And cement paste of shotcrete which are made in 2006 were also analyzed. In this pH of shotcrete is lower than other in situ concrete since accelerating agent may act as decreasing factor of pH. (3) An experiment which investigates dissolution of HFSC cement hydrates to ground water around Horonobe URL. According to the experiment, dissolving depth of HFSC is 4 times small comparing to Ordinary Portland Cement hydrates after 30th water exchange.

JAEA Reports

Study on applicability of low alkaline cement in Horonobe Underground Research Laboratory Project, 2 (Contract research)

Nakayama, Masashi; Kobayashi, Yasushi; Matsuda, Takeshi*; Noda, Masaru*; Iriya, Keishiro*; Takeda, Nobufumi*

JAEA-Research 2009-035, 70 Pages, 2009/11

JAEA-Research-2009-035.pdf:11.27MB

In Horonobe Underground Research Center construction of underground facility began in 2005 and construction practicality test with HFSC (Highly Fly-ash contained Silica-fume Cement) is planned in a part of the gallery. Before HFSC will be placed in the gallery it is necessary to validate that HFSC has performance under the actual construction. The research results in 2007 were as follows. As corrosion behavior in HFSC, reinforced concrete specimen with HFSC 226 have been exposed to off-shore condition at in saline water and splashed zone and analyzed corrosion rate and chloride intrusion, and they were summarized. Service life time of HFSC reinforced concrete was assessed more than 50 years until cracking due to corrosion is generated. pH and components of solid and liquid phase which were made in 2002, and stored in water were analyzed. And cement paste of shotcrete which are made in 2006 were also analyzed. In this pH of shotcrete is lower than other in situ concrete since accelerating agent may act as decreasing factor of pH. The results obtained from this ten year's study were summarized on shotcerete, in situ concrete and grouting. Based on the summery, method of quality control, such as testing method, frequency, and standards so on, were investigated.

JAEA Reports

Studies on the design method of multi tunnels in geological disposal facility, 2

Hayashi, Katsuhiko; Kobayashi, Yasushi; Hiramoto, Masayuki*; Mizutani, Kazuhiko*; Morita, Atsushi*

JAEA-Research 2009-016, 127 Pages, 2009/08

JAEA-Research-2009-016.pdf:5.23MB

"Study on configuration of analytical domain of the multi tunnels model" and "Remainders on an elasto-plastic FEM (Finite Element Method) analysis" in case of the full width of pillar become plastic on simplified model" are studied as "The study on the enhanced reliability of elasto-plastic FEM". In addition, "The effect of rock support and consolidation of the host rock to control the plastic region" was conducted as "The study on the mechanical stability of tunnels". As the results, it was seen that the analytical domain should be assigned 3-5W (W: width of multi tunnels) for a horizontal side from the endmost tunnel and 3-4W for below of the tunnels. It was found reasonable and proper on the elasto-plastic FEM analysis that the analysis domain must be large enough not to have plastic deformation in all analysis of domains under the condition in which the full width of pillar has plastic deformation. It was also found that the ground support suppresses the plasticity domain as the ground support effect. It was acknowledged that the auxiliary construction method by improvement of the ground has the suppression effect of the plasticity domain applying to the multi tunnels.

Journal Articles

Durability evalation of steel reinforced low alkaline concrete using pozzolanic reaction based on exposure test in off-shore

Takeda, Nobufumi*; Kuwae, Hitomi*; Nakayama, Masashi; Kobayashi, Yasushi

Konkurito Kogaku Nenji Rombunshu (DVD-ROM), 31(1), p.895 - 900, 2009/07

High level radioactive waste repository will be constructed using a variety of concrete such as shotcrete, lining for rock support. It is anticipated that highly alkaline plume released from the cement hydrates could influence the long-term performance of barrier system as a result of degradation of the buffer material and rock. In order to reduce hyper alkaline, JAEA is now undertaking development of low alkaline cement (HFSC: Highly Fly ash contained Silicafume Cement). In this report, to evaluate corrosion behavior of reinforcement in HFSC, we have conducted exposure test using reinforced concrete specimens in off-shore condition for 6 years, investigated corrosion rate and permeation chloride ion in concrete. As the result, it is evaluated that the period until crack occurred is more than 30 years in case of using HFSC concrete.

JAEA Reports

Application study on low alkaline cementitious materials for deep geological repository of high level radioactive wastes, 2; Organization of previous finding and understanding of material properties of low alkaline cement (Joint research)

Kobayashi, Yasushi; Yamada, Tsutomu; Naito, Morimasa; Yui, Mikazu; Nakayama, Masashi; Sato, Haruo; Nishida, Takahiro*; Hironaga, Michihiko*; Yamamoto, Takeshi*; Sugiyama, Daisuke*; et al.

JAEA-Research 2009-013, 70 Pages, 2009/06

JAEA-Research-2009-013.pdf:8.85MB

Cementitious materials will be used to ensure construction and operational safety and work efficiency in a deep geological repository. The low alkaline cement has been developed to reduce uncertainties due to hyper alkaline for the long-term safety performance of the repository system. Functions of cementitious material required in each phase of repository construction, operation and closure were summarized in a separate report entitled "Application Study on Low Alkaline Cementitious Materials for Deep Geological Repository of High Level Radioactive Wastes (Phase I) "In this report, properties of low alkaline cement/concrete which have been developed both at home and abroad, and recipes of the low alkaline concrete taken account of application to the repository component have been investigated. Fresh and hardened properties of the low alkaline cement are equivalent to the OPC and the low alkaline cement has an advantage over OPC in terms of leaching resistance. The HFSC developed by JAEA, which belongs to a pozzolanic type low alkaline cement will be able to apply to the shotcrete and the lining concrete by choosing an adequate recipe. Clarification of influences of the chemical composition of groundwater on leachate properties of the hydrates, examination of pH measurement of cement leachate, evaluation of corrosion behavior of rebar embedded in the HFSC concrete are raised as open questions for future activities.

JAEA Reports

Horonobe Underground Research Laboratory project research and development plan in Phase 2; H20-21

Iwatsuki, Teruki; Sato, Haruo; Tanai, Kenji; Inagaki, Manabu; Sawada, Atsushi; Niinuma, Hiroaki; Ishii, Eiichi; Maekawa, Keisuke; Tomura, Goji; Sanada, Hiroyuki; et al.

JAEA-Research 2009-002, 156 Pages, 2009/05

JAEA-Research-2009-002.pdf:12.86MB

The research and development plan for geological investigation, engineering technology and safety assessment during the drilling of a shaft down to intermediate depth are summarized according to the Midterm Plan till 2009 Fiscal year of JAEA. This report describes subject, current status and programme in the "Phase 2: Construction phase" (investigations during construction of the underground facilities). Furthermore regarding R&D plan in next Midterm Plan of JAEA, preliminary ideas are summarized.

JAEA Reports

Application study on low alkaline cementitious materials for deep geological repository of high level radioactive wastes, 1; Requirements for use of cementitious materials in deep geological repository system (Joint research)

Kobayashi, Yasushi; Yamada, Tsutomu; Naito, Morimasa; Yui, Mikazu; Nakayama, Masashi; Sato, Haruo; Nishida, Takahiro*; Hironaga, Michihiko*; Yamamoto, Takeshi*; Sugiyama, Daisuke*; et al.

JAEA-Research 2008-112, 43 Pages, 2009/03

JAEA-Research-2008-112.pdf:4.58MB

In deep geological repository, use of cementitious material for rock support, lining, and grouting is essential for construction and operation and possibly raises in groundwater pH due to leachate from the cements. Since this hyperalkaline condition may lead to degradation of barriers, there is concern that it gives significant impact on long-term safety performance of the repository system. Because of these backgrounds, developments of low alkaline cement have been conducted both at home and abroad. JAEA is now planning to conduct an in-situ test for shotcreting using low alkaline cement at the Horonobe URL. On the other hand, CRIEPI has studied and developed cementitious materials for disposal of radioactive wastes. This joint research report summarizes requirements and expected performance of cementitious materials in repository taking account of surrounding conditions in each stage of the repository program so as to reflect them to further development of the low alkaline cement.

JAEA Reports

Studies about strength recovery and generalized relaxation behavior of rock, 2 (Contract research)

Okubo, Seisuke*; Hayashi, Katsuhiko; Kobayashi, Yasushi; Hiramoto, Masayuki*

JAEA-Research 2008-106, 91 Pages, 2009/02

JAEA-Research-2008-106.pdf:6.08MB

It is generally known that the rock has the properties of strength recovery by elapse of time around the tunnel inside sedimentary rock with ground support due to inner pressure and ground pressure. The properties of strength recovery must be taken into account of the estimation about cavity shape stability or the long-term dynamical behavior of closed disposal ground. Our research study is focusing on the properties of strength recovery, generalized relaxation behavior and the characteristics of tensile strength by experiments using boring cores obtained from the Horonobe Underground Research Laboratory so as to improve the modeling for future stage.

JAEA Reports

Study on applicability of low alkaline cement in Horonobe Underground Research Laboratory Project (Contract research)

Matsuda, Takeshi*; Noda, Masaru*; Iriya, Keishiro*; Konishi, Kazuhiro*; Nakayama, Masashi; Kobayashi, Yasushi

JAEA-Research 2007-089, 139 Pages, 2008/05

JAEA-Research-2007-089.pdf:13.57MB

In Horonobe Underground Research Center construction of underground facility began in 2005 and construction practicality test with HFSC (Highly Fly-ash contained Silica-fume Cement) is planned in a part of the gallery. Before the HFSC will be contracted in the gallery it is necessary to check that the HFSC has performance under the actual construction. The main work of this Japanese fiscal year is making a detailed test plan for the HSFC construction practicality, that is scheduled after 2007 and laboratory tests on lowering behavior of pH in the HFSC concrete were conducted. On the construction practicality test with low alkaline concrete, HFSC in-situ experiment plan was studied in case using HSFC424N as shotcrete. The aims of the in-situ test are the validation in applicability of low alkaline concrete as a support member for underground opening in the realistic geological environment and building the method to evaluate influence to the surrounding geological environment. The location of the in-situ test is in the connection tunnel of a depth of 140m and the geology is the Koetoi formation. The period of the test is approximately 10 years. The test plan was designed to be able to make a comparison with Ordinary Portland Cement. As it is necessary to confirm the strength property of the HFSC concrete with materials procured at construction site, strength of the base concrete using local procured fine aggregate and coarse aggregate based on the result of the selection of mix proportion in 2005 research was checked. On laboratory tests on lowering behavior of pH in HFSC concrete, the pH of immersion fluid was measured and components of the immersion fluid and the solid phase were analyzed using test specimens in a long-term immersion test which had been continued since 2005.

JAEA Reports

A Study for improvement of the credibility of evaluation method for the long-term dynamical behavior of near-field rock mass, 2; A Study for the influence of inner pressures caused by buffer material and overpack

Hiramoto, Masayuki; Kobayashi, Yasushi; Aoyagi, Shigeo*; Miyanomae, Shunichi*

JAEA-Research 2008-013, 62 Pages, 2008/03

JAEA-Research-2008-013.pdf:9.17MB

For improvement of the credibility of evaluation method for the long-term dynamical behavior of near-field rock mass, the influence that swelling pressure caused by buffer material and expansion pressure caused by the erosion of overpack gave long-term stability of near-field rock mass was studied in this report. As a result, because swelling pressure caused by buffer material and expansion pressure caused by the erosion of overpack acted on near-field rock mass as inner pressure, long-term stability of near-field rock mass improved. And it was shown that conventional evaluation method gave results of safe side. But as an exception, when stiffness property of buffer material is large and initial stress of rock mass is small, a possibility that tensile fracture occurred in near field rock mass was shown. In such a case, a possibility that functional decline of artificial barrier happens is concerned, because buffer material flows out into the crack that occurred in rock mass.

JAEA Reports

Studies about strength recovery and generalized relaxation behavior of rock (Contract research)

Hiramoto, Masayuki; Kobayashi, Yasushi; Okubo, Seisuke*

JAEA-Research 2008-002, 60 Pages, 2008/03

JAEA-Research-2008-002.pdf:2.52MB

Strength recovery and generalized relaxation behavior of rock were examined. The sample rock was Wakkanai-formation shale. In Chapter 2, strength recovery characteristic of rocks was examined. It was found that strength recovery increases with increase of testing time or load-holding time. It was interesting that the sample with relatively small unconfined compressive strength showed higher strength recovery. These results were obtained for only two sample rocks. Therefore, the accumulation of the data is needed in future to evaluate the influence of the boring places quantitatively. In Chapter 3, the generalized relaxation behavior of rock was examined. As a result, scatter in obtained data is considerably large, so the accumulation of the data is needed in future to understand rightly the complicated generalized relaxation behavior.

JAEA Reports

Studies on the design method of multi tunnels in geological disposal facility

Hiramoto, Masayuki; Kobayashi, Yasushi; Nakama, Shigeo; Mizutani, Kazuhiko*; Morita, Atsushi*

JAEA-Research 2008-001, 84 Pages, 2008/03

JAEA-Research-2008-001.pdf:13.19MB

In this study, the following studies on the design method of multi-tunnels were performed. Study on the outbreak behavior of EDZ (Chapter 2) Study on the stability evaluation of the pillars (Chapter 3) In Chapter 2, analysis was carried out for "multi-tunnels model" that modeled the gallery group of a disposal panel scale. As a result, it is important to use multi-tunnels models for prediction evaluation of EDZ, because the outbreak behavior of EDZ was different from the model of the H12 report. In Chapter 3, a stability evaluation method of pillars was considered from two viewpoints of "pillar strength" and "pillar load" based on the similar structures. As a result, if numerical analysis by the multi-tunnels model was carried out, pillar strength and pillar load was estimated adequately. Therefore, a stability evaluation method of the pillars in a disposal institution was suggested.

JAEA Reports

Development and management of the knowledge base for the geological disposal technology; Annual report 2006

Umeda, Koji; Oi, Takao; Osawa, Hideaki; Oyama, Takuya; Oda, Chie; Kamei, Gento; Kuji, Masayoshi*; Kurosawa, Hideki; Kobayashi, Yasushi; Sasaki, Yasuo; et al.

JAEA-Review 2007-050, 82 Pages, 2007/12

JAEA-Review-2007-050.pdf:28.56MB

This report shows the annual report which shows the summarized results and topic outline of each project on geological disposal technology in the fiscal year of 2006.

JAEA Reports

Key points of disturbances caused by engineering materials used in the phase of repository construction from the viewpoints of long-term system performance

Yamada, Tsutomu; Hiramoto, Masayuki; Kobayashi, Yasushi; Yui, Mikazu; Sato, Haruo; Matsui, Hiroya

JAEA-Review 2007-008, 44 Pages, 2007/03

JAEA-Review-2007-008.pdf:4.76MB

Disturbances caused by construction and operation of the ONKALO (the underground rock characterization facility in Olkiluoto) have been studied by POSIVA in Finland. In this study, engineering and stray materials which might influence the long-term system performance were discussed taking account of the results of POSIVA study and materials to used for the construction of the Horonobe URL, and then summarized for the future stage of repository construction.

JAEA Reports

In situ test plan for concrete materials using low alkaline cement at Horonobe URL

Kobayashi, Yasushi; Yamada, Tsutomu; Nakayama, Masashi; Matsui, Hiroya; Matsuda, Takeshi*; Konishi, Kazuhiro*; Iriya, Keishiro*; Noda, Masaru*

JAEA-Review 2007-007, 42 Pages, 2007/03

JAEA-Review-2007-007.pdf:3.12MB

Shotcrete and lining will be used for safety under construction and operational period in HLW repository. Concrete is a kind of composite material which is constituted by aggregate, cement and other mixture. Low alkaline cement has been developed from the viewpoint of long term stability of the barrier systems which would be influenced by high alkaline arising from cement material. HFSC is one of a low alkaline cement. It has been developed in Japan Atomic Energy Agency. JAEA are now implementing the construction of the under ground research laboratory (URL) at Horonobe. This report shows the in situ test plan for shotcrete using HFSC at Horonobe URL with identifying requirements for cement materials to be used in HLW repository, and also reviews major literatures of low alkaline cement. This in situ test plan is aiming to assess the performance of HFSC shotcrete in terms of mechanics, workability, durability, and so on.

JAEA Reports

Horonobe Underground Research Laboratory project synthesis of phase I investigation 2001-2005 volume "Geological Disposal Research"

Fujita, Tomoo; Taniguchi, Naoki; Matsui, Hiroya; Tanai, Kenji; Nishimura, Mayuka; Kobayashi, Yasushi; Hiramoto, Masayuki; Maekawa, Keisuke; Sawada, Atsushi; Makino, Hitoshi; et al.

JAEA-Research 2007-045, 140 Pages, 2007/03

JAEA-Research-2007-045-1.pdf:38.33MB
JAEA-Research-2007-045-2.pdf:44.62MB

This report summarizes the progress of research and development on geological disposal during the surface-based investigation phase (2001-2005) in the Horonobe Underground Research Laboratory project (HOR), of which aims are to apply the design methods of geological disposal and mass transport analysis to actual geological environments and derive future subjects based on the results. The design methods of geological disposal were reviewed based on the recent knowledge and the advertences were identified. Then the parameters for virtual design of engineered barrier system, backfill deposition hole and tunnel were set up based on actual geological conditions obtained from the surface-based investigations in HOR as an example of actual geological environment. The conceptual structure from site investigation and evaluation to mass transport analysis was represented as a work flow at first. Then following this work flow a series of procedures for mass transport analysis were carried out based on actual geological conditions obtained from the surface-based investigations in HOR to illustrate the functioning of the work flow and the applicability of this methodology. Consequently, knowledge that will help follow-up or future execution and planning activities was obtained.

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