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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.
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.
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.
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.
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.
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.
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.
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.
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:38.33MBJAEA-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.
Hiramoto, Masayuki; Kobayashi, Yasushi; Aoyagi, Shigeo*; Miyanomae, Shunichi*; Morita, Atsushi*
JAEA-Research 2007-003, 54 Pages, 2007/03
JAEA-Research-2007-003.pdf:3.67MB
For the study on the long-term stability of near-field rock mass, the following studies were carried out in this report. (1) Inspection of applicability of a valuable-compliance-type constitutive equation that used the measurement data of the existing tunnel. (2) Suggestion of the informatization construction that used a valuable-compliance-type constitutive equation (1) FEM model was developed to estimate the time dependet behavior of rock mass surrounding tunnel. The calculated results such as tunnel convergence and the axial force exerted on tunnel support were compared with the measured results in-situ. It was found that the calculated results reasonably well coincided with the measured results. (2) The informatization construction that used a valuable-compliance-type constitutive equation was suggested. This method will be used for disposal ground construction. It will be led to improving reliability of long-term evaluation after closedown.