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Kawata, Kento*; Ogata, Sho*; Aoyagi, Kazuhei; Ozaki, Yusuke; Iwai, Hiromasa*; Yasuhara, Hideaki*
Dai-51-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu(Internet), p.113 - 118, 2025/12
In the deep geological disposal of High-Level Waste, it is essential to understand the fracturing behavior of the rock mass surrounding the disposal tunnel due to excavation for assessing the safety of the repository. In this study, 2D tunnel excavation analysis models based on damage theory were developed and were applied to an in-situ tunnel excavation conducted at Horonobe Underground Research Laboratory. The results of the analysis were then compared with in-situ data available on the purpose of validation. As a result, 18 different analysis models were constructed by changing model parameters, and two models that exhibited the best agreement with the measured data were proposed.
Asahina, Daisuke*; Takamura, Hiroaki*; Tsukamoto, Koji*; Honda, Fumito*; ITO, Takashi*; IWATA, Naoki*; Aydan, 
mer*; Sato, Toshinori
Dai-51-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu(Internet), p.43 - 47, 2025/12
Fault zones commonly contain distinctive structures such as fault cores and damage zones, where physical properties vary locally. These zones are important for evaluating underground safety and groundwater flow in waste disposal, yet quantitative measurements near faults remain limited. We applied Schmidt hammer and needle penetration tests to assess the mechanical properties of the rocks near the Tanakura Fault, in a simple, non-destructive manner. The results showed a clear spatial variation in measured values with distance from the fault gouge boundary, suggesting that combining methods with different scales and sensitivities can provide a more comprehensive evaluation of rock mass properties near faults.
Ozaki, Yusuke; Ogata, Sho*; Nakaoka, Kenichi*; Shimizu, Hiroyuki*; Yasuhara, Hideaki*; Akaki, Toshifumi*; Aoyagi, Kazuhei; Fukuda, Daisuke*
Dai-51-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu(Internet), p.125 - 130, 2025/12
The Subcommittee on Research of Coupled Phenomena in Rock, under the Japan Society of Civil Engineers, conducts coupled numerical simulations using various approaches by participating members. The evaluation of the excavation damaged zone (EDZ) in the Horonobe Underground Research Laboratory using hydro-mechanical coupled simulation is one of the tasks of the subcommittee. In this presentation, the problem statement, modeling approaches, and current results from participating organizations are summarized.
Aoyagi, Kazuhei; Tamura, Tomonori; Ozaki, Yusuke; Ishii, Eiichi; Motoshima, Takayuki*; Sugawara, Kentaro*
Dai-51-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu(Internet), p.119 - 124, 2025/12
In a high-level radioactive waste disposal, it is important to understand the extent of the Excavation Damaged Zone (EDZ) because it can be one of the factors to determine whether disposal galleries or pits can be excavated or not in the design or construction phases. In this study, we performed a hydro-mechanical coupling analysis to simulate the three-dimensional excavation of the twin galleries which were excavated at a depth of 500 m in the Horonobe Underground Research Laboratory. The analysis revealed that the EDZ was developed 1.5-2.0 m from the gallery wall. The stress acting on the shotcrete was within the ultimate limit state. Based on these results, we estimated that the stability of the twin galleries will be maintained, despite the relatively large extent of the EDZ.