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Sanada, Hiroyuki; Matsui, Hiroya; Ogawa, Toyokazu*; Kinomura, Koji*; Aoki, Tomoyuki*; Yamamoto, Takuya*
JAEA-Research 2009-050, 57 Pages, 2010/01
It is important to understand EDZ in assessing performance of repository and designing of plug. It is known that it remains possible that the large-scale EDZ is generated due to strain localization from boring investigations and tunnel excavation analyses and rock properties changes with increase of depth. Excavation analysis of vertical shaft in sedimentary rock taken into account strain softening, depth variation of rock properties and the actual construction procedure had been done in order to understand EDZ of Horonobe URL. The large-scale EDZ due to strain localization was generated around the border between Koetoi formation and Wakkanai formation. From result obtained from excavation analysis, scale of EDZ obtained from excavation analysis is from 60 cm to 120 cm. And it was estimated that seismic velocity changed by 20 percent, elastic modulus changed by 30 percent and hydraulic conductivity changed by 0.1 m/s order.
Ogawa, Toyokazu*; Kinomura, Koji*; Aoki, Tomoyuki*; Yamamoto, Takuya*; Sanada, Hiroyuki; Matsui, Hiroya
Dai-12-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.933 - 940, 2008/09
Japan Atomic Energy Agency is planning to conduct researches into geological disposal of high-level radioactive wastes in the Horonobe site located in Hokkaido, Japan. As part of the underground research facilities, two 500m-long vertical shafts have been constructed in tertiary sedimentary rocks since 2005. The surrounding rocks are known to exhibit strain-softening characteristics, necessitating appropriate modelling in the stability analysis. In addition the rocks physical properties often vary with depth. This study shows the results of three-dimensional numerical analysis of the ventilation shaft, taking the construction sequence and the variation of rock properties with depth into consideration.
Ogawa, Toyokazu*; Kinomura, Koji*; Aoki, Tomoyuki*; Yamamoto, Takuya*; Matsui, Hiroya; Sanada, Hiroyuki
Dai-37-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu (CD-ROM), p.301 - 306, 2008/01
no abstracts in English
Kinomura, Koji*; Ogawa, Toyokazu*; Aoki, Tomoyuki*; Yamamoto, Takuya*; Matsui, Hiroya; Sanada, Hiroyuki
Dai-37-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu (CD-ROM), p.307 - 312, 2008/01
no abstracts in English
Sanada, Hiroyuki; Matsui, Hiroya; Yamamoto, Takuya*; Aoki, Tomoyuki*; Ogawa, Toyokazu*; Jo, Mayumi*; Fujii, Yoshiaki*
Heisei-19-Nendo Shigen, Sozai Gakkai Hokkaido Shibu Sokai Oyobi Shunki Koenkai Koen Yoshishu, p.9 - 10, 2007/06
Japan Atomic Energy Agency has been conducting the Horonobe Underground Reseach Laboratory Project as a part of geological isolation research and development at Horonobe-town in Hokkaido, Japan. The rocks around URL have high porosity and low permeability. Therefore, the excess pore pressure caused by URL excavation is possible to affect to the stability of surrounding rock. In this point of view, the authors carried out a stress-seepage coupled analysis to understand the process of the pore pressure change due to excavation and the influence to the stability of surrounding rock and support system. As a result, the large excess pore pressure causes a part in surrounding rock on excavation in an anisotropic initial stress condition and it dissipates with time. The pore pressure change causes the complex deformation in the surrounding rock as well. However, the phenomena are not significant influence to the stability of the surrounding rock and support system.
Ogawa, Toyokazu*; Aoki, Tomoyuki*; Jo, Mayumi*; Matsui, Hiroya; Horii, Hideyuki*
Dai-36-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu, p.39 - 44, 2007/01
In case rock exhibits time-dependent deformation, it is important to evaluate this effect on the tunnel stability, since the rock deforms elastically as well as inelatically even at the time of excavation. This paper introduces an engineering approach method to explain the effect of time-dependent deformation of rock at tunnel excavation stages on the stability. The mechanical parameters to describe a Burgers type rheological model are determined, based upon the drained triaxial creep test results performed on mudstone samples. With the parameters determined, plane-strain 2 dimensional numerical analyses are subsequently performed. In the analysis a couple of indices to describe the degree and timing of time-dependent deformation are introduced with reference to the instantaneous elastic deformation, and their effects on the amount of deformation and support pressure subsequent to the support erection are investigated.
Ogawa, Toyokazu*; Matsui, Hiroya
JNC TN8400 2005-011, 157 Pages, 2005/02
Horonobe Underground Research Center has been conducting researches and developments into geological disposal of high-level radioactive wastes in sedimentary rocks. In the 2003 borehole investigation programmes, 3 boreholes (HDB-6, 7, and 8) were drilled in order to acquire geoscientific information. This technical report presents the results of elastic wave velocity measurements under confining pressure, carried out on the rock cores extracted from BH HDB-6. The main observations which became clear from the laboratory tests are as follows: 1. the basic physical properties of the rock specimens are consistent with the existing measured values. Moreover, when the wet sample is dried, although P wave velocity at first shows a downward tendency, it increases gradually and approaches the dry velocity as the degree of saturation decreases. Therefore, it is felt that the sample is uniformly dried across the cross-sectional area. ; 2. It appears that the elastic wave velocities of the Horonobe sedimentary rocks are dependent upon pressure. However shear rigidity remains unchanged, even if the saturation conditions of pores change (from wet to dry conditions). In the study of anisotropy of velocities, horizontal velocity seems larger than the vertical one. Although there was no remarkable influence on elastic wave velocities when the loading and unloading of confining pressure were repeated, a certain amount of hysteresis could be observed in porosity. Continuous investigation is required. ; 3. Measured wet velocity may practically be used in evaluating in-situ velocity measurement results.
Ogawa, Toyokazu; Uchida, Masahiro
JNC TN8510 2004-001, 31 Pages, 2004/03
In this technical material, OECD/NEA's 2001 report "The Role of Underground Laboratories in Nuclear Waste Disposal Programmes" has been translated into Japanese. The purpose of the material preparation was to make the translated version a useful reference as regard to the design and construction of deep underground laboratories to be built in Tono and in Horonobe.
Ogawa, Toyokazu; Uchida, Masahiro
JNC TN8510 2003-001, 249 Pages, 2004/03
As a reference for the design and construction of deep underground laboratories to be built in Tono and in Horonobe, SKB's technical report TR01-29 which deals with the site investigations was partially translated into Japanese. This material covers the overall philosophy of site investigations and execution methodologies in discipline-specific areas of hydrology, geochemistry, material transport, and surface ecosystems.
; Ogawa, Toyokazu; Inoue, Hiroyuki*;
JNC TN8400 2002-015, 65 Pages, 2002/05
For the safety assessment of geological waste disposal system, it is imperative to understand the long-term mechanical deformation characteristics of the near field rock mass. In the assessment, it is important to take into account that the rock mass will be subjected to different environments that will change with the progress of time: during construction; during operation of waste package burial; and after confinement. Among possible factors that may affect the long-term mechanical deformation characteristics of rock mass, there are nainly two factors investigated in this report: the effects of alternating dry and wet conditions (during construction); and the thermal effect (during the emplacement of waste packages). Mudstone samples are first exposed to dry and wet cycles, and/or to elevated ternperature conditions. Constant strain rate uniaxial compression tests are subsequently carried out on the samples. Test results of the uniaxial compression tests show: (1)Strength of the mudstone decreases and the deformation characteristics change due to dry and wet cycles. (2)Strength decreases slightly, and the deformation characteristics change a little due to pre-heat treatment. Effect is however small. Also discussed in the report is necessity of a numerical prediction analysis with the use of the experimental results on the two factors studied.
Ogawa, Toyokazu*; Aoki, Tomoyuki*; Kinomura, Koji*; Matsui, Hiroya
no journal, ,
no abstracts in English
Ogawa, Toyokazu*; Aoki, Tomoyuki*; Kinomura, Koji*; Sanada, Hiroyuki; Matsui, Hiroya
no journal, ,
no abstracts in English