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Journal Articles

Extending water retention curves to a quasi-saturated zone subjected to a high water pressure up to 1.5 Megapascals

Sakaki, Toshihiro*; Komatsu, Mitsuru*; Takeuchi, Ryuji

Vadose Zone Journal (Internet), 15(8), 7 Pages, 2016/08

 Times Cited Count:1 Percentile:91.59(Environmental Sciences)

In the Groundwater Recovery Experiment in Tunnel which is underway at the MIU, water saturation is one of the key parameters to monitor in order to understand the recovery processes. In this study, the process of saturation increase in the quasi-saturated zone where trapped discrete air phase affects saturation due to further increase in water pressure was studied. The relationship between the positive water pressure and saturation was measured by laboratory test using sands with trapped air bubbles and the effect of compression of bubbles on the changes in saturation was analyzed. The experimental results showed that the water pressure-saturation curves closely followed the relationship estimated solely based on the air bubble compression using Boyle's law. Based on this observation, a mathematical model was established to define the water pressure - saturation curve for the region where the water pressure is positive.

JAEA Reports

Developing the soil moisture sensor using optical fiber technique (Joint research)

Komatsu, Mitsuru*; Nishigaki, Makoto*; Seno, Shoji*; Hirata, Yoichi*; Takenobu, Kazuyoshi*; Tagishi, Hirotaka*; Kunimaru, Takanori; Maekawa, Keisuke; Yamamoto, Yoichi; Toida, Masaru*; et al.

JAEA-Research 2012-001, 77 Pages, 2012/09

JAEA-Research-2012-001.pdf:4.85MB

This research focused on methods of estimating the amounts of groundwater recharge, which are normally required as upper boundary conditions in groundwater flow analyses, based on measurements of infiltrating water in the ground, to systematize the methods and establish systems which are stable and measurable on site over a long time. Regarding developing measurement systems, fiber-optic strain measurement methods that enable multiple-point and long-distance measurement were used for measuring three quantities: suction pressure, soil moisture and volumetric water content rate obtained by applying water absorption swelling material, and each measurement was discussed. The results showed that the fiber-optic soil aquameter has two types of practical application: one for measuring suction pressure (Type I), and the other for measuring volumetric water content rate obtained by applying water absorption swelling material (Type III). Furthermore, by using measurement instruments in actual fields, the validity of the two methods for estimating the rainfall infiltration capacities of shallow-layer soils, that is, estimating the capacities either directly by measurements of soil water or from unsaturated hydraulic conductivities, was confirmed.

Journal Articles

Estimation of infiltration amount from in-situ moisture measuring method in shallow ground

Komatsu, Mitsuru*; Nishigaki, Makoto*; Seno, Shoji*; Toida, Masaru*; Tagishi, Hirotaka*; Takenobu, Kazuyoshi*; Yamamoto, Yoichi

Chikasui Jiban Kankyo Ni Kansuru Shimpojium 2011 Happyo Rombunshu (CD-ROM), p.17 - 26, 2011/11

no abstracts in English

Journal Articles

Monitoring of pore water pressure and water content around a horizontal drift through excavation; Measurement at the 140m gallery in the Horonobe URL

Yabuuchi, Satoshi; Kunimaru, Takanori; Kishi, Atsuyasu*; Komatsu, Mitsuru*

Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 67(4), p.464 - 473, 2011/11

Japan Atomic Energy Agency has been conducting the Horonobe Underground Research Laboratory (URL) project in Horonobe, Hokkaido, as a part of the research and development program on geological disposal of high-level radioactive waste. Pore water pressure and water content around a horizontal drift in the URL have been monitored for over 18 months since before the drift excavation was started. During the drift excavation, both pore water pressure and water content were decreasing. Pore water pressure has been still positive though it continued to decrease with its gradient gradually smaller after excavation, while water content turned to increase about 6 months after the completion of the excavation. It turned to fall again about 5 months later. An unsaturated zone may have been in homogeneously formed around the horizontal drift considering a degassing.

JAEA Reports

Study on the Mechanism of the Unsaturated Zone in Rock Mass

Sugita, Yutaka; Kikuchi, Hirohito*; Komatsu, Mitsuru*; Nishigaki, Makoto*; Akagi, Yosuke*

JNC-TY8400 2003-011, 143 Pages, 2002/02

JNC-TY8400-2003-011.pdf:4.19MB

In geological disposal of high-level radioactive waste (HLW), unsaturated zone will be expected to appear around the disposal tunnel due to the construction of the tunnel. Cooperative research between JNC and Okayama University has done to understand the mechanism of the unsaturation process and the re-saturation process around the tunnel from FY1998 to FY2000.Characterizing Laboratory test on Unsaturated zonE (CLUE) of JNC was used to simulate the unsaturation process, and the piezometer and frequency domain reflectometry (FDR) of Okayama University were used to measure the unsaturation behavior of the CLUE.During this study, the laboratory experiments were performed and the saturation-unsaturation hydraulic characteristics of the material were obtained. The applicability of the FDR to measure the unsaturation condition was examined. Unsaturation hydraulic analysis technique was also applied.These studies supplied the fundamental data on unsaturation processes around the tunnel.

JAEA Reports

Experimental studies on unsaturated zone surrounding rock using Characterizing Laboratory test on Unsaturated zonE(CLUE)

Kikuchi, Hirohito*; Sugita, Yutaka; Chijimatsu, Masakazu*; Suzuki, Hideaki*; Komatsu, Mitsuru*; Nishigaki, Makoto*

JNC-TN8400 2002-004, 97 Pages, 2002/02

JNC-TN8400-2002-004.pdf:4.28MB

In geological disposal of high-level radioactive waste (HLW), unsaturated zone will be developed around the disposal tunnel due to the construction of the tunnel. The development of the unsaturated zone would lead to the intrusion of the air into the surrounding rock and then oxygen would dissolve into ground water. Dissolved air affects the redox potential of the ground water and also oxidizes minerals existed in surrounding rock and changes their sorption capacity. These influences would change the geochemical conditions of the repository and affect the corrosion behavior of the overpack. Therefore, Characterizing Laboratory test on Unsaturated zonE (CLUE) was designed and assembled to understand the development process of the unsaturated zone. The CLUE is designed from the viewpoint of the hydraulic characteristics. CLUE has two test tanks. The test tank A uses glass beads to simulate rock mass, the test tank B uses rock block sample. Fundamental hydraulic data of the glass beads on saturation/unsaturation conditions for numerical analysis was obtained. Tests using the test tank A used the piezometer and frequency domain reflectometry (FDR) to measure the unsaturation behavior. From the results of the test tank A, the unsaturated zone was developed around the tunnel. The piezometer and FDR measured the distribution and the time history of the unsaturated zone well. In stable condition, measurement data was in good agreement with the analytical results.

Oral presentation

Study on measuring method for infiltrating behavior of compacted bentonite material using Frequency Domain Reflectometry

Komatsu, Mitsuru*; Nishigaki, Makoto*; Chijimatsu, Masakazu*; Nakama, Shigeo

no journal, , 

no abstracts in English

Oral presentation

Study on measurement of soil moisture content by using the optical fiber pressure sensor

Komatsu, Mitsuru*; Nishigaki, Makoto*; Seno, Shoji*; Hirata, Yoichi*; Kunimaru, Takanori

no journal, , 

no abstracts in English

Oral presentation

Water content monitoring during the excavation of the horizontal drift in the Horonobe Underground Research Laboratory Project

Yabuuchi, Satoshi; Kishi, Atsuyasu*; Komatsu, Mitsuru*

no journal, , 

no abstracts in English

Oral presentation

Estimating of in-situ hydraulic conductivity related with evaluating of rainfall infiltration behavior in shallow ground

Komatsu, Mitsuru*; Nishigaki, Makoto*; Seno, Shoji*; Tagishi, Hirotaka*; Takenobu, Kazuyoshi*; Kishi, Atsuyasu

no journal, , 

Infiltration rate at the ground surface is one of the essential boundary conditions for a quantitative evaluation of groundwater flow. Conventional method for quantifying infiltration rate based on the water budget, however, includes significant uncertainties resulting from different types of quantities to be measured. In this study, focusing on a method where the infiltration rate is estimated directly from temporal changes in soil water contents in the region of interest, the measurement data was confirmed based on the ${it in-situ}$ unsaturated hydraulic tests. Then, the reliability of the measurement was verified by comparing the ${it in-situ}$ data to the laboratory test results and uncertainties associated with the ${it in-situ}$ measurements were quantified.

Oral presentation

Confirmation of the performance test of the optical fiber moisture metering sensor

Seno, Shoji*; Komatsu, Mitsuru*; Nishigaki, Makoto*; Tagishi, Hirotaka*; Takenobu, Kazuyoshi*; Kishi, Atsuyasu

no journal, , 

The soil moisture measurement method is being developed with the application of the optical fiber sensor, that is thought to be more advantageous than the conventional methods in the soil moisture measurement regarding its characteristics of multiple-point and long-distance measurement. We report the results obtained in the performance test of the optical fiber moisture metering sensor in the course where its fundamental mechanism and its principle are being developed.

Oral presentation

In-situ moisture monitoring methods for the sedimentary rocks as affected by groundwater salinity

Komatsu, Mitsuru*; Kishi, Atsuyasu; Tsukuda, Akie*

no journal, , 

In this study, with the goal of applicability an in-situ measurement technique for monitoring generation and extension of the unsaturated zone around a drift, a set of water content measurement was carried out for the core samples collected during the excavation of pilot survey drift in a sedimentary rock formation. For the drill core collected under brine environment the Horonobe deep underground laboratory, FDR-V method was applied. FDR-V measures complex permittivity from reflection characteristic in the coaxial cable tip using an electromagnetic wave with high frequency. The results showed that the effects of the salinity on the measurement were insignificant.

Oral presentation

In-situ moisture monitoring methods for the sedimentary rocks as affected by temperature

Tsukuda, Akie*; Komatsu, Mitsuru*; Kishi, Atsuyasu

no journal, , 

In this study, with the goal of applicability an in-situ measurement technique for monitoring generation of the unsaturated zone around a drift and performance of the artificial barrier, a set of water content measurement was carried out for the core samples collected during the excavation of pilot survey drift in a sedimentary rock formation. For the drill core collected Koetoi layer, FDR-V method was applied. FDR-V measures complex permittivity from reflection characteristic in the coaxial cable tip using an electromagnetic wave with high frequency. The results showed that the effects of the temperature on the measurement were insignificant.

13 (Records 1-13 displayed on this page)
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