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JAEA Reports

Poro-elastic parameter acquisition test using siliceous mudstone (Wakkanai formation)

Aoki, Tomoyuki*; Tani, Takuya*; Sakai, Kazuo*; Koga, Yoshihisa*; Aoyagi, Kazuhei; Ishii, Eiichi

JAEA-Research 2020-002, 83 Pages, 2020/06

JAEA-Research-2020-002.pdf:8.25MB
JAEA-Research-2020-002-appendix(CD-ROM).zip:6.63MB

The Japan Atomic Energy Agency (JAEA) has conducted with the Horonobe Underground Research Project in Horonobe, Teshio-gun, Hokkaido for the purpose of research and development related to geological disposal technology for high-level radioactive wastes in sedimentary soft rocks. The geology around the Horonobe Underground Research Laboratory (HURL) is composed of the Koetoi diatomaceous mudstone layer and the Wakkanai siliceous layer, both of which contain a large amount of diatom fossils. Since these rocks exhibit relatively high porosity but low permeability, it is important to investigate the poro-elastic characteristics of the rock mass. For this objective, it is necessary to measure parameters based on the poro-elastic theory. However, there are few measurement results of the poro-elastic parameters for the geology around HURL, and the characteristics such as dependence on confining pressure are not clearly understood. One of the reasons is that the rocks show low permeability and the pressure control during testing is difficult. Therefore, a poro-elastic parameter measurement test was conducted on the siliceous mudstone of the Wakkanai formation to accumulate measurement results on the poro-elastic parameters and to examine the dependence of the parameters on confining pressure. As a result, some dependency of the poro-elastic parameters on confining pressure was observed. Among the measured or calculated poro-elastic parameters, the drained bulk modulus increased, while the Skempton's pressure coefficient, and the Biot-Wills coefficient in the elastic region decreased with the increase in confining pressure. The measurement results also inferred that the foliation observed in the rock specimens might impact a degree of dependency of those parameters on confining pressure.

Journal Articles

Effects of magnetic field and pressure on the valence-fluctuating antiferromagnetic compound EuPt$$_2$$Si$$_2$$

Takeuchi, Tetsuya*; Yara, Tomoyuki*; Ashitomi, Yosuke*; Iha, Wataru*; Kakihana, Masashi*; Nakashima, Miho*; Amako, Yasushi*; Honda, Fuminori*; Homma, Yoshiya*; Aoki, Dai*; et al.

Journal of the Physical Society of Japan, 87(7), p.074709_1 - 074709_14, 2018/07

 Times Cited Count:12 Percentile:65.34(Physics, Multidisciplinary)

Journal Articles

Electronic states in EuCu$$_2$$(Ge$$_{1-x}$$Si$$_x$$)$$_2$$ based on the doniach phase diagram

Iha, Wataru*; Yara, Tomoyuki*; Ashitomi, Yosuke*; Kakihana, Masashi*; Takeuchi, Tetsuya*; Honda, Fuminori*; Nakamura, Ai*; Aoki, Dai*; Gochi, Jun*; Uwatoko, Yoshiya*; et al.

Journal of the Physical Society of Japan, 87(6), p.064706_1 - 064706_14, 2018/06

 Times Cited Count:18 Percentile:75.94(Physics, Multidisciplinary)

Journal Articles

Rock spalling and countermeasures in shaft sinking at the Horonobe Underground Research Laboratory

Tsusaka, Kimikazu; Inagaki, Daisuke; Nago, Makito*; Aoki, Tomoyuki*; Shigehiro, Michiko*

Proceedings of 6th International Symposium on In-situ Rock Stress (RS 2013) (CD-ROM), p.339 - 346, 2013/08

The Horonobe Underground Research Laboratory is planned to consist of the Ventilation Shaft (4.5 m in diameter), the East and West Access Shafts (6.5 m in diameter). The host rock of the URL site comprises Neogene sedimentary rocks. The unconfined compressive strength of the rocks is less than 20 MPa on average. Anisotropic stress distribution around the URL is also confirmed. Because several highly permeable fractures (hydraulic transmissivity: approximately 10$$^{-5}$$m$$^{2}$$/s) with the size greater than the shaft diameter develop under the condition of around 2 in competence factor (i.e., the ratio of the unconfined compressive strength of rock to the initial stress) below a depth of 250 m, shaft sinking is a challenging issue from the viewpoint of tunnel engineering in the Horonobe URL Project. In this paper, the construction of the Ventilation Shaft below a depth of 250 m at the Horonobe URL is reported. During shaft sinking, fracture mapping of the shaft wall was performed. The geometry of the shaft wall was also measured using a three-dimensional laser scanner in order to investigate the shape and volume of rock spalling in the shaft wall resulting from the excavation work. Rock spalling was predominantly observed on the south and north wall rock corresponding to the direction of the minimum horizontal initial stress. A large amount of rock spalling also developed along a large-scale fault. With respect to the lining span and the layout of rockbolts, several support patterns were designed and installed as the countermeasures to prevent the development of excessive rock spalling. A flowchart for selecting the optimum support design was then developed.

JAEA Reports

Excavation analysis of vertical shaft in sedimentary rock taken into account strain softening and depth variation of rock properties

Sanada, Hiroyuki; Matsui, Hiroya; Ogawa, Toyokazu*; Kinomura, Koji*; Aoki, Tomoyuki*; Yamamoto, Takuya*

JAEA-Research 2009-050, 57 Pages, 2010/01

JAEA-Research-2009-050.pdf:8.14MB

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.

Journal Articles

Excavation analysis of vertical shaft in sedimentary rock at great depth, taking into account variation in rock physical properties with depth

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.

Journal Articles

Long-term behaviors of a tuunel in a sedimentary soft rock due to fluid-mechanical interaction

Aoki, Tomoyuki*; Sanada, Hiroyuki; Jo, Mayumi*; Yamamoto, Takuya*; Matsui, Hiroya

Dai-12-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.709 - 716, 2008/09

Long-term behaviors of a tunnel at great depth in sedimentary soft rocks are investigated based on pore fluid-mechanical interaction. Poroelastic parameters of diatomaceous and siliceous mudstones at the Horonobe URL site are determined from the tests proposed in this study using a triaxial test apparatus. The test procedures with their theoretical base are described. Coupled fluid-mechanical behaviors on circular and horse-shoe-shaped tunnels supported with shotcrete are numerically analyzed based on the theory of poroelasticity. Some long-term behaviors of rocks and supports peculiar to the fluid-mechanical interaction differing from creep behavior are found from the analysis results.

Journal Articles

Celebration of 30th anniversary of the experimental fast reactor Joyo

Nakai, Satoru; Aoyama, Takafumi; Ito, Chikara; Yamamoto, Masaya; Iijima, Minoru; Nagaoki, Yoshihiro; Kobayashi, Atsuko; Onoda, Yuichi; Ohgama, Kazuya; Uwaba, Tomoyuki; et al.

Kosoku Jikkenro "Joyo" Rinkai 30-Shunen Kinen Hokokukai Oyobi Gijutsu Koenkai, 154 Pages, 2008/06

no abstracts in English

Journal Articles

Evaluation on stability of shaft during excavation, considerating strain softening behavior surrounding rock mass

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

Journal Articles

Numerical simulation of borehole shape, focusing on strain localization

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

Journal Articles

Consideration on poroelastic behavior of siliceous rock mass around an opening by stress-seepage coupled analysis

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.

Journal Articles

Stability analysis of underground opening during excavation, taking time-dependent behaviour of surrounding rock mass into consideration

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.

JAEA Reports

Investigation on time-dependent behavior of sedimentary rock (Phase 3)

Yamamoto, Takuya*; Aoki, Tomoyuki*; Jo, Mayumi*

JNC TJ5400 2005-002, 200 Pages, 2005/03

JNC-TJ5400-2005-002.pdf:42.65MB

For the rational design of the underground facility and for the safety during construction and operation it is necessary to consider the long-term stability of the rock mass around a drift. Especially, the time-dependent behavior of sedimentary rock is important because the mechanism of time-dipenednt is not well understood. Here, laboratory tests of rock specimens collected from the borehole investigation and numerical analysis on the stability of the rock mass around a drift were discussed for last two years. In this year, additional laboratory tests were performed to confirm the several important knowledges for last two years. Moreover, the preliminary numerical analysis was carried out to predict the EDZ due to excavation of underground facility.

JAEA Reports

Investigation on time-depedent behavior of sedimentary rock, 2

Yamamoto, Takuya*; Aoki, Tomoyuki*; Taki, Haruo*; Jo, Mayumi*

JNC TJ5400 2003-005, 190 Pages, 2004/02

JNC-TJ5400-2003-005.pdf:37.41MB

none

JAEA Reports

Investigation on time-dependent behavior of sedimentary rock

Yamamoto, Takuya*; Aoki, Tomoyuki*; Taki, Haruo*; Jo, Mayumi*

JNC TJ5400 2003-001, 120 Pages, 2003/06

JNC-TJ5400-2003-001.pdf:14.04MB

none

JAEA Reports

None

Yamamoto, Takuya*; Aoki, Tomoyuki*; Taki, Haruo*

JNC TJ1400 2001-007, 186 Pages, 2002/03

JNC-TJ1400-2001-007.pdf:5.49MB

no abstracts in English

JAEA Reports

Investigation on time-depedent behavior of sedimentary rock, 2

Yamamoto, Takuya*; Aoki, Tomoyuki*; Taki, Haruo*; Jo, Mayumi*

JNC TJ5400 2003-004, 73 Pages, 2000/02

JNC-TJ5400-2003-004.pdf:8.3MB

none

JAEA Reports

None

Shimo, Michito*; Yamamoto, Takuya*; Yamamoto, Hajime*; Aoki, Tomoyuki*

PNC TJ7205 97-002, 42 Pages, 1997/10

PNC-TJ7205-97-002.pdf:1.28MB

None

JAEA Reports

None

Shimo, Michito*; Ijiri, Yuji*; Aoki, Tomoyuki*; Sugihara, Yutaka*

PNC TJ7205 95-001, 189 Pages, 1995/03

PNC-TJ7205-95-001.pdf:9.78MB

None

JAEA Reports

None

Shimo, Michito*; Aoki, Tomoyuki*; Ijiri, Yuji*; Sugihara, Yutaka*

PNC TJ7205 94-001, 180 Pages, 1994/05

PNC-TJ7205-94-001.pdf:9.36MB

no abstracts in English

27 (Records 1-20 displayed on this page)