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Nara, Yoshitaka*; Kashiwaya, Koki*; Oketani, Kazuki*; Fujii, Hirokazu*; Zhao, Y.*; Kato, Masaji*; Aoyagi, Kazuhei; Ozaki, Yusuke; Matsui, Hiroya; Kono, Masanori*
Zairyo, 73(3), p.220 - 225, 2024/03
The fractures in the rock are the main pass of groundwater flow and solute transport. The filling of fine-grained particle, such as clay minerals, was confirmed to decrease the permeability of rock by laboratory experiment. This research aimed to verify the occurrence of the phenomena in the field. The water containing the clay minerals was injected into the rock at the 200m stage of the Mizunami Underground research laboratory. The hydraulic conductivity decreased two order before and after the injection. This result suggested that the decrease of hydraulic conductivity by the filling of fine-grained particle in the fractures occurred in the real field.
Ozaki, Yusuke; Ono, Hirokazu; Aoyagi, Kazuhei
Shigen, Sozai Koenshu (Internet), 6 Pages, 2023/09
In the Horonobe Underground Research Laboratory, the in-situ experiment for performance confirmation of engineered barrier system was performed at the 350 m stage to develop the technology for geological disposal. Several measurements have been conducted in and around the test drift to investigate the time dependent impact of the experiment on the rock and backfilled tunnel. Some measurement results are introduced in this presentation.
Ozaki, Hirokazu*; Yoshimura, Kazuya; Asaoka, Yoshihiro*; Hayashi, Seiji*
Environmental Monitoring and Assessment, 193(6), p.369_1 - 369_9, 2021/06
Times Cited Count：6 Percentile：40.04(Environmental Sciences)Matsui, Hiroya; Ozaki, Yusuke; Uyama, Masao*; Fujii, Hirokazu*
no journal, ,
no abstracts in English
Ozaki, Hirokazu*; Yoshimura, Kazuya; Katayose, Yuji*; Matsumoto, Takumi*; Asaoka, Yoshihiro*; Hayashi, Seiji*
no journal, ,
no abstracts in English
Ozaki, Hirokazu*; Hayashi, Seiji*; Yoshimura, Kazuya; Katayose, Yuji*; Matsumoto, Takumi*; Asaoka, Yoshihiro*
no journal, ,
no abstracts in English
Cs discharge characteristics from a forested catchment of the Ohta RiverSakuma, Kazuyuki; Yoshimura, Kazuya; Nakanishi, Takahiro; Funaki, Hironori; Tsuruta, Tadahiko; Ochi, Kotaro; Hayashi, Seiji*; Tsuji, Hideki*; Ozaki, Hirokazu*
no journal, ,
Cesium-137 leaching from decomposing forest litter is thought to be one pathway by which dissolved Cs enters rivers from forests. To clarify whether this process contributes or not, we studied the correlation between humin-like matter from microorganism-induced plants decomposition and dissolved Cs concentrations. River water samples were collected approximately once a month from April 2017 to August 2019 at 10 locations (7 locations from April 2019) from the upstream of the Ohta River in the Namie and Minamisoma districts. These samples were filtered through 0.45-
m-pore size membrane filters. The dissolved Cs concentrations and fluorescence intensities of humin-like matter were measured. A positive correlation was found between the fluorescence intensities of humin-like matter and normalized dissolved Cs concentration (R
= 0.17, p 
0.001). The results indicate that Cs leaching from forest litter because of litter decomposition can contribute to increasing the dissolved Cs concentration in river water in forested catchments.
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.
Kamata, Kento*; Nara, Yoshitaka*; Matsui, Hiroya; Ozaki, Yusuke; Fujii, Hirokazu*; Zhao, Y.*
no journal, ,
In this study, we perform a carbonated water injection experiment into the fractured rock to investigate the reduction of permeability due to the sealing of fractures by the precipitation of carbonated minerals at the 350m stage in Horonobe URL. We drilled a 80cm borehole from the drift wall and injected the carbonated water into the fractures there in the excavated damaged zone. The hydraulic test that we performed regularly during the injection experiment indicates the reduction of hydraulic conductivity slightly. To understand the mechanism of the reduction of permeability, we plan to analyze the core sample collected by overcoring.
Kamata, Kento*; Nara, Yoshitaka*; Kashiwaya, Koki*; Tada, Yohei*; Fujii, Hirokazu*; Zhao, Y.*; Matsui, Hiroya; Ozaki, Yusuke
no journal, ,
We conducted a carbonated water injection experiment at 350m stage in Horonobe URL. Two boreholes with 1m were drilled from drift wall and carbonated water was injected. The cement material powder was added one of the boreholes. The hydraulic conductivity around the borehole where only carbonated water was injected slightly decreased. The hydraulic conductivity around the borehole where both cement material powder and carbonated water decreased and increased because of the clogging of fracture by the powder and dissipation of it.
Kuwabara, Shogo*; Nara, Yoshitaka*; Kashiwaya, Koki*; Fujii, Hirokazu*; Zhao, Y.*; Matsui, Hiroya; Ozaki, Yusuke; Hiroyoshi, Naoki*
no journal, ,
This study aims to develop a healing method of fractured rock by injection of cement powder and carbonated water to form carbonated minerals. The in-situ hydraulic tests were carried out to confirm the effect of their injection into rock. The decrease of hydraulic conductivity was recognized after the injection of both cement powder and carbonated water, whereas the injection of only carbonated water did not induce the decrease of hydraulic conductivity.
