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Aoyagi, Kazuhei; Ishii, Eiichi
Environmental Earth Sciences, 83(3), p.98_1 - 98_15, 2024/02
Times Cited Count：0 Percentile：0.04(Environmental Sciences)The long-term geological disposal of high-level radioactive waste relies on predictions of future changes in a disposal facility's hydro-mechanical characteristics to assess potential leakage through fractures in the excavation damaged zone (EDZ) after backfilling the facility. This study evaluated the transmissivity of EDZ fractures using in situ hydraulic tests around the area of a full-scale, experimental, engineered barrier system in the Horonobe Underground Research Laboratory, Hokkaido, Japan. After their installation, the buffer blocks swelled, altering the stresses within the EDZ fractures. The effects of these changing stresses on the fractures' transmissivity were assessed over a period of 4 years. The transmissivity continuously decreased in this period to about 41% of its value measured prior to the swelling. Using the Barton-Bandis normal-stress-dependent fracture-closure model, the decrease in transmissivity is quantitatively attributed to closure of the EDZ fractures, which was caused by the swelling pressure increasing up to 0.88 MPa. Evidence of fracture closure came from seismic tomography surveying, which revealed a slight increase in seismic velocity in the study area with increasing swelling pressure. The results show that EDZ fractures were closed by swelling of the full-scale buffer material. They also demonstrate the applicability of the Barton-Bandis model to preliminary estimation of the long-term transmissivity of EDZ fractures in facilities for the geological disposal of radioactive waste.
Hata, Koji*; Nyunoya, Sumio*; Aoyagi, Kazuhei; Miyara, Nobukatsu
Doboku Gakkai Rombunshu, F1 (Tonneru Kogaku) (Internet), 77(2), p.I_29 - I_43, 2021/00
no abstracts in English
Aoyagi, Kazuhei; Sakurai, Akitaka; Tanai, Kenji
Dai-46-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.142 - 147, 2019/01
This research presents the hydro-mechanical behavior of EDZ in shaft sinking in the Horonobe underground Research Laboratory on the basis of the results of in situ hydraulic tests, acoustic emission (AE) measurements, and hydro-mechanical coupling numerical analysis. The AE sources were distributed within 1.5 m into the shaft wall; and hydraulic conductivity in the EDZ is 2 to 4 orders of magnitudes higher than that in no fractured area. On the other hand, on the basis of the result of numerical analysis, the maximum extent of the EDZ is 1.5 m into the gallery wall. This result is almost consistent with the trend of acoustic emission measurement and hydraulic test.
Aoyagi, Kazuhei; Nago, Makito*
Jiban Kogakkai-Shi, 65(8), p.12 - 15, 2017/08
In this paper, we described the development of the supporting tool of observational construction of the underground research laboratory, and the monitoring result of hydro-mechanical properties around the gallery wall. As an observational construction tool, we developed a "3D geological structure/construction data visualization system". The geological data, measurement data, construction data, and prediction analysis results are visualized and integrated comprehensively as the construction proceeds. The planned support pattern was examined according to the visualized data. In addition, the Excavation Damaged Zone (EDZ) was extended within 1.0 m from the gallery wall. In this area, hydraulic conductivity was enhanced. However, the extent of the EDZ was not enlarged along with time; the stability of the support was also confirmed on the basis of the measurement of stress in the shotcrete. Integrating these results the observational construction considering the development of an EDZ can be established. This technology will have an important role in geological disposal of high-level radioactive waste.
Aoyagi, Kazuhei; Ishii, Eiichi; Nakayama, Masashi; Fujita, Tomoo
Nihon Zairyo Gakkai Dai-65-Ki Tsujo Sokai, Gakujutsu Koenkai Rombunshu (USB Flash Drive), p.19 - 20, 2016/05
no abstracts in English
*; Kaji, Yoshiyuki; *; *
Nihon Kikai Gakkai Rombunshu, A, 57(542), p.2349 - 2354, 1991/10
no abstracts in English
Suzuki, K.; Katano, Y.; Aruga, T.; Hamada, S.; Shiraishi, K.
Journal of Nuclear Materials, 133-134, p.585 - 589, 1985/00
Times Cited Count：2 Percentile：37.51(Materials Science, Multidisciplinary)no abstracts in English
; Katano, Y.; Aruga, T.; Shiraishi, K.
JAERI-M 84-181, 37 Pages, 1984/10
no abstracts in English
Aoyagi, Kazuhei; Ishii, Eiichi; Ishida, Tsuyoshi*
no journal, ,
no abstracts in English
Kubota, Kenji*; Oyama, Takahiro*; Suenaga, Hiroshi*; Nohara, Shintaro*; Aoyagi, Kazuhei; Sugita, Yutaka
no journal, ,
no abstracts in English
Kamata, Kento*; Nara, Yoshitaka*; Fujii, Hirokazu*; Zhao, Y.*; Matsui, Hiroya; Ozaki, Yusuke
no journal, ,
The precipitation of carbonate minerals in rock is expected to close the fracture opening. In Horonobe URL, we perform the carbonated water injection test to heal the EDZ by the carbonate mineral precipitation. We compare the permeability before and after the injection to evaluate the closure of fractures in the EDZ. The significant change in permeability is not recognized at the present due to the short injection period and continuous injection would be required to change the permeability of EDZ by the precipitation.
Goke, Mitsuo*; Okihara, Mitsunobu*; Toguri, Satohito*; Matsui, Hiroya; Ozaki, Yusuke; Mochizuki, Akihito; Maemura, Tsuneyuki*; Ito, Ryo*
no journal, ,
The report summarized the overview and the results of mechanical simulation about a case study for long term changing of the geological environment around a drift in Horonobe URL.
Ito, Ryo*; Maemura, Tsuneyuki*; Matsui, Hiroya; Ozaki, Yusuke; Mochizuki, Akihito; Goke, Mitsuo*; Okihara, Mitsunobu*; Toguri, Satohito*
no journal, ,
The report summarized the hydrological simulation about a case study for long term changing of the geological environment around a drift in Horonobe URL.
Kubota, Kenji*; Morifuji, Yohei*; Oyama, Takahiro*; Matsui, Hiroya
no journal, ,
This report summarize the results of resistivity tomography around the drifts during 10 years after the excavation in Horonobe URL and investigation of core samples within the tomography region.
