A Proposed method to discriminate a gas derived from deep underground by focusing on the relationship between changes in methane and carbon dioxide concentrations in the atmosphere

Miyakawa, Kazuya; Shimo, Michito*; Niwa, Masakazu; Amano, Kenji; Tokunaga, Tomochika*; Tonokura, Kenichi*

Fukada Chishitsu Kenkyujo Nempo, (22), p.139 - 153, 2021/00

no abstracts in English

Rapid identification of water-conducting fractures using a trace methane gas measurement

Niwa, Masakazu; Amano, Kenji; Takeuchi, Ryuji; Shimada, Koji

Groundwater Monitoring & Remediation, 41(3), p.41 - 50, 2021/00

https://doi.org/10.1111/gwmr.12428

Identification of water-conducting fractures is important for the safety assessment of underground projects in crystalline rocks at geological disposal sites. We applied a portable methane gas analyzer by wavelength-scanned cavity ring-down spectroscopy to detect the water-conducting fractures in an underground tunnel excavated in granite with CH-rich groundwater. Two approaches were taken to obtain the profile of CH concentration along the gallery walls: (1) Scan by walking at the speed of 0.5 m/s and (2) monitoring for 30 s at 0.5 or 1-m intervals. In the Scan by walking approach, the peaks of the CH concentration corresponded well with the occurrence of high water flow rate fractures. Thus, this method is useful for rapid identification of major water-conducting fractures. Monitoring at constant intervals takes more time than the Scan by walking approach; however, this method can largely detect occurrences of fractures with low fluid fluxes.

3D geostatistical modeling of fracture system in a granitic massif to characterize hydraulic properties and fracture distribution

Koike, Katsuaki*; Kubo, Taiki*; Liu, C.*; Masoud, A.*; Amano, Kenji; Kurihara, Arata*; Matsuoka, Toshiyuki; Lanyon, B.*

Tectonophysics, 660, p.1 - 16, 2015/10

https://doi.org/10.1016/j.tecto.2015.06.008

This study integrates 3D models of rock fractures from different sources and hydraulic properties aimed at identifying relationships between fractures and permeability. A geostatistical method (GEOFRAC) that can incorporate orientations of sampled data was applied to 50,900 borehole fractures for spatial modeling of fractures over a 12 km by 8 km area, to a depth of 1.5 km. GEOFRAC produced a plausible 3D fracture model, in that the orientations of simulated fractures correspond to those of the sample data and the continuous fractures appeared near a known fault. Small-scale fracture distributions with dominant orientations were also characterized around the two shafts using fracture data from the shaft walls. By integrating the 3D model of hydraulic conductivity using sequential Gaussian simulation with the GEOFRAC fractures from the borehole data, the fracture sizes and directions that strongly affect permeable features were identified.

Precise topographic analysis using 10m grid DEM in the Horonobe area

Sakai, Toshihiro; Matsuoka, Toshiyuki; Amano, Kenji

JAEA-Data/Code 2014-005, 43 Pages, 2014/05

JAEA-Data-Code-2014-005.pdf:33.23MB
JAEA-Data-Code-2014-005-appendix(DVD).zip:940.62MB

The Horonobe Underground Research Laboratory (URL) Project is being pursued by the Japan Atomic Energy Agency (JAEA) at Horonobe-cho in Northern Hokkaido, Japan. One of the main goals of the URL project is to establish techniques for investigation, analysis and assessment of the deep geological environment. As a part of this URL project, we develop the geological environment modeling technique. 10m grid digital elevation model (DEM) had been published by Geographical Survey Institute in 2008. The use of 10m grid DEM has made possible examination of detailed topographical features in wide area. We created eighteen kinds of filterd image data using 10m grid DEM around the Horonobe-cho to obtain the basic information for evaluating topographical and geological features and constructing the geological environment model.

Construction of evaluation model for rainwater cultivation amount

Munakata, Masahiro; Amano, Kenji; Tanaka, Tadao

JNES-RE-2013-9032, p.63 - 78, 2014/02

http://www.nsr.go.jp/archive/jnes/content/000126924.pdf

no abstracts in English

Study on development of evaluation technique of in-situ tracer test in Horonobe Underground Research Laboratory Project (Contract research)

Yokota, Hideharu; Amano, Kenji; Maekawa, Keisuke; Kunimaru, Takanori; Naemura, Yumi*; Ijiri, Yuji*; Motoshima, Takayuki*; Suzuki, Shunichi*; Teshima, Kazufumi*

JAEA-Research 2013-002, 281 Pages, 2013/06

JAEA-Research-2013-002.pdf:13.03MB

To evaluate permeable heterogeneity in a fracture and scale effects which are problems to be solved based on the mass transportation data of fractures in hostrock, a number of tracer tests are simulated in a fictitious single plate fracture generated on computer in this study. And the transport parameters, e.g. longitudinal dispersion length, true velocity and dilution rate, are identified by fitting one- and two-dimensional models to the breakthrough curves obtained from the simulations in order to investigate the applicability of these models to the evaluation of tracer test. As a result, one-dimensional model yields larger longitudinal dispersion length than two-dimensional model in the both cases of homogeneous and heterogeneous hydraulic conductivity fields of the fictitious fracture. And, the longitudinal dispersion length identified from a tracer test is smaller and/or larger than the macroscopic longitudinal dispersion length identified from whole fracture. It is clarified that these are occurred by shorter or longer distance between boreholes compare to the correlation length of geostatistical heterogeneity of fictitious fracture.

Geological investigations for geological model of deep underground geoenvironment at the Mizunami Underground Research Laboratory (MIU)

Tsuruta, Tadahiko; Tagami, Masahiko; Amano, Kenji; Matsuoka, Toshiyuki; Kurihara, Arata; Yamada, Yasuhiro*; Koike, Katsuaki*

Chishitsugaku Zasshi, 119(2), p.59 - 74, 2013/02

https://doi.org/10.5575/geosoc.2011.0010

Japan Atomic Energy Agency (JAEA) is developing a geoscientific research project, Mizunami Underground Research Laboratory (MIU) project, in order to establish scientific and technological basis for geological disposal of HLW. A series of geological mapping, reflection seismic survey, borehole investigation and geological investigations around research galleries are carried out to identify the distribution and the heterogeneity of fractures and faults that are potential major flow-pass of groundwater as field investigations. This paper describes geological investigations in the MIU project, focused on the evaluation of their effectiveness in order to understand the deep underground geological environment.

Fault zone determination and bedrock classification through multivariate analysis; Case study using a dataset from a deep borehole in the Mizunami Underground Research Laboratory

Abumi, Kensho*; Amano, Kenji; Koike, Katsuaki*; Tsuruta, Tadahiko; Matsuoka, Toshiyuki

Joho Chishitsu, 22(4), p.171 - 188, 2011/12

https://doi.org/10.6010/geoinformatics.22.171

Fault zones are treated as essential elements for evaluating the underground geological environment and the engineering performance of rocks. Because of the limitations to borehole investigations, it is not always possible to obtain sufficient, high-quality geological data. In addition, the evaluation of results may differ depending on various factors such as geological conditions and skill of the engineer. Such uncertainty can lead to difficulty in evaluation and understanding of the geological environment at depths and in the decision-making and planning of underground construction, which, as a result, may increases potential risks during construction. To reduce the uncertainty, this study proposes a correct selection method of data item for multivariable analyses composed of principal component analysis and clustering method using a deep borehole data. Utilizing this method and the analyses, the rocks could be accurately classified depending upon their geological characteristics.

Development of comprehensive techniques for coastal site characterisation; Integrated palaeohydrogeological approach for development of site evolution models

Amano, Kenji; Niizato, Tadafumi; Ota, Kunio; Lanyon, B.*; Alexander, W. R.*

Proceedings of 14th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2011) (CD-ROM), p.1477 - 1481, 2011/09

https://doi.org/10.1115/ICEM2011-59259

The assurance of the long-term stability of the geological environment is for deep geological disposal. In Japan, since uplift/subsidence and climatic and sea-level changes would result in a significant change to hydraulic and hydrochemical conditions at coastal sites, it is of importance to establish comprehensive techniques for characterising the overall evolution of coastal sites over geological time. To this end, modelling techniques focussing on the coastal site evolution have been developed through the collaborative research programme at the Horonobe coastal study area. A palaeohydrogeological conceptual model has been developed based on all available information and eventually key geological properties and processes as well as a methodology for appropriately defining the initial and boundary conditions for long-term groundwater flow simulations have been clarified.

Development of comprehensive techniques for coastal site characterisation, 1; Strategic overview

Ota, Kunio; Amano, Kenji; Niizato, Tadafumi; Alexander, W. R.*; Yamanaka, Yoshiaki*

Proceedings of 13th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2010) (CD-ROM), p.123 - 132, 2010/10

https://doi.org/10.1115/ICEM2010-40056

The assurance of the long-term stability of the geological environment is for deep geological disposal. In Japan, since uplift/subsidence and climatic and sea-level changes would result in a significant change to hydraulic and hydrochemical conditions at coastal sites, it is of importance to establish comprehensive techniques for characterising the overall evolution of coastal sites over geological time. To this end, palaeohydrogeological study is ongoing in the coastal area around Horonobe in northern Hokkaido. A "Geosynthesis Data Flow Diagram" defining a methodology for characterising the palaeohydrogeological evolution of the site has been formulated and, based on the geosynthesis methodology, a basic strategy has been established for stepwise investigations from initial survey of existing information to the final borehole programme at any coastal site. This technique has now been tested and optimised with the progress of the investigations.