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Mochizuki, Akihito; Matsui, Hiroya; Nakayama, Masashi; Sakamoto, Ryo*; Shibata, Masahito*; Motoshima, Takayuki*; Jo, Mayumi*
Case Studies in Construction Materials, 22, p.e04648_1 - e04648_20, 2025/07
Times Cited Count：0The properties of low-pH cement used in the geological disposal of radioactive waste may change through atmospheric carbonation and degradation caused by groundwater during the long-term operation of a repository. In this study, we investigated the effects of atmospheric carbonation and groundwater contact on the chemical, microstructural, and transport properties of shotcrete made from low-pH, high-fly-ash silica-fume cement (HFSC) over a period of 16 years in an underground research laboratory. In both carbonated and degraded zones of the HFSC shotcrete, capillary porosity increased for pores of 
300 nm in diameter, and the total porosity was higher than in undegraded zones. These changes in porosity may be associated with the decalcification of calcium-silicate-hydrate and decomposition of ettringite. Such changes were minor in altered zones of OPC shotcrete, indicating that HFSC shotcrete is less resistant to atmospheric carbonation and groundwater leaching under the studied conditions. However, the hydraulic conductivity in HFSC was low enough to fulfill the specific functional requirements of low-pH cements for geological disposal.
Yoshida, Hidekazu*; Yamamoto, Koshi*; Asahara, Yoshihiro*; Maruyama, Ippei*; Karukaya, Koichi*; Saito, Akane*; Matsui, Hiroya; Mochizuki, Akihito; Jo, Mayumi*; Katsuta, Nagayoshi*; et al.
Communications Engineering (Internet), 3, p.67_1 - 67_10, 2024/05
A capability to permanently seal fluid flow-paths through bedrock, like boreholes or underground tunnels, is needed to ensure the long-term safety and effectiveness of many underground activities e.g. CO
storage, hydrocarbon field abandonment, and nuclear waste disposal. Commonly used cementitious seals may not be sufficiently durable due to chemical and physical degradation. Learning from natural calcite (CaCO
) concretion formation, a more durable sealing method was developed using a "concretion-forming solvent". The method was tested by sealing flow-paths next to a tunnel in an underground research laboratory at 350 meters depth. The flow-paths initially sealed rapidly, then resealed after disturbance by earthquakes (M5.4). The treated rock recovered its very low natural permeability, demonstrating permanent sealing that is robust.
Tomota, Yo*; Ojima, Mayumi*; Harjo, S.; Gong, W.*; Sato, Shigeo*; Ung
r, T.*
Materials Science & Engineering A, 743, p.32 - 39, 2019/01
Times Cited Count：37 Percentile：84.91(Nanoscience & Nanotechnology)Jo, Mayumi*; Ono, Makoto*; Nakayama, Masashi; Asano, Hidekazu*; Ishii, Tomoko*
Geological Society Special Publications, 482, 16 Pages, 2018/09
Times Cited Count：4 Percentile：34.09(Geology)Xu, P. G.; Harjo, S.; Ojima, Mayumi*; Suzuki, Hiroshi; Ito, Takayoshi*; Gong, W.; Vogel, S. C.*; Inoue, Junya*; Tomota, Yo*; Aizawa, Kazuya; et al.
Journal of Applied Crystallography, 51(3), p.746 - 760, 2018/06
Times Cited Count：28 Percentile：89.55(Chemistry, Multidisciplinary)Tsusaka, Kimikazu*; Inagaki, Daisuke*; Niunoya, Sumio*; Jo, Mayumi*
Proceedings of 8th Asian Rock Mechanics Symposium (ARMS-8) (USB Flash Drive), 9 Pages, 2014/10
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.
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.
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.
Yamamoto, Takuya*; Aoki, Tomoyuki*; Taki, Haruo*; Jo, Mayumi*
JNC TJ5400 2003-005, 190 Pages, 2004/02
JNC-TJ5400-2003-005.pdf:37.41MB
none
Yamamoto, Takuya*; Aoki, Tomoyuki*; Taki, Haruo*; Jo, Mayumi*
JNC TJ5400 2003-001, 120 Pages, 2003/06
JNC-TJ5400-2003-001.pdf:14.04MB
none
Shimo, Michito*; Yamamoto, Hajime*; Jo, Mayumi*; Yamagami, Masahito*; Fumimura, Kenichi*; Kumamoto, So*; Igarashi, Takafumi*
JNC TJ7440 2005-083, 991 Pages, 2003/01
JNC-TJ7440-2005-083.PDF:130.74MB
None
Yamamoto, Takuya*; Aoki, Tomoyuki*; Taki, Haruo*; Jo, Mayumi*
JNC TJ5400 2003-004, 73 Pages, 2000/02
none
Xu, P. G.; Harjo, S.; Ojima, Mayumi*; Ito, Takayoshi*; Gong, W.*; Suzuki, Hiroshi; Akita, Koichi; Inoue, Junya*; Tomota, Yo*; Aizawa, Kazuya
no journal, ,
Jo, Mayumi*; Iwatani, Takafumi*; Kawakubo, Masahiro*; Ishii, Tomoko*; Ono, Makoto*; Nakayama, Masashi
no journal, ,
For the purpose of "maintaining the soundness of the artificial barrier", we are studying "restraints on the outflow of the buffer material". We conducted an experiment of a scale of 30 cm to 1 m in an actual underground environment and confirmed the occurrence of the buffer material outflow under water inflow conditions. The experiment in this study was undertaken in order to acquire the necessary data for considering a method to control the outflow of the buffer material.
Motoshima, Takayuki*; Jo, Mayumi*; Iso, Sachie*; Shirase, Mitsuyasu*; Kobayashi, Masato*; Nakayama, Masashi
no journal, ,
Radioactive waste needs to be managed responsibly even after the waste is transported to the final disposal site. Reversibility and retrievability are also required in high level radioactive waste disposal project. From the viewpoint of the technical feasibility of the retrievability, the development of a technology for removing the bentonite backfilling material surrounding the PEM without damaging the PEM is expected. In this paper, we selected the liquid removal technology using the water jet method and verified the feasibility of selected technology in Horonobe URL, depth of 350 meters.
Jo, Mayumi*; Motoshima, Takayuki*; Iso, Sachie*; Shirase, Mitsuyasu*; Kobayashi, Masato*; Nakayama, Masashi
no journal, ,
Radioactive waste needs to be managed responsibly even after the waste is transported to the final disposal site. Reversibility and retrievability are also required in high level radioactive waste disposal project. From the viewpoint of the technical feasibility of the retrievability, the development of a technology for removing the bentonite backfilling material surrounding the PEM without damaging the PEM is expected. In this paper, we selected the mechanical removal technology using the auger method and verified the feasibility of selected technology in Horonobe URL, depth of 350 meters.
Xu, P. G.; Ojima, Mayumi*; Inoue, Junya*; Shiro, Ayumi; Akita, Koichi; Nambu, Shoichi*; Suzuki, Hiroshi; Harjo, S.; Gong, W.; Tomota, Yo; et al.
no journal, ,
Xu, P. G.; Ojima, Mayumi*; Suzuki, Hiroshi; Nambu, Shoichi*; Inoue, Junya*; Onuki, Yusuke*; Harjo, S.; Akita, Koichi
no journal, ,
