Nishiyama, Nariaki; Kawamura, Makoto; Umeda, Koji*; Niwa, Masakazu
Oyo Chishitsu, 64(3), p.98 - 111, 2023/08
It is important to accumulate research examples on the spatial distribution of dikes under volcanic edifices for risk assessment in volcanic disaster prevention and site selection and safety assessment for the geological disposal of high-level radioactive waste. The topography of volcanoes is considered to represent the location of magma intrusion associated with volcanic activity and its history. In this study, we attempted to determine the predominant orientation of radial dikes and evaluate the central conduit stability based on the distribution, centroid, and area of contour lines comprising the volcanic edifices using GIS-based topographic analysis. As a result of the topographic analysis, the predominant orientation of the dikes was successfully shown for the volcanoes with stable conduits. On the other hand, this analysis was not suitable for determine the predominant orientation of dikes in volcanoes with unstable conduits, thus the applicable range of this analysis is considered to be determined by the conduit stability. In addition, the conduit stability can be evaluated by using the area data of contour polygons, which represents the scope of application to the method for determination of the predominant orientation of dikes. This means that the conduit stability during volcanic activity can be evaluated even for volcanoes of which activity history is not yet known, and that topographic analysis is a useful tool for this purpose. The use of topographic analysis in this study will be expected to provide a new scale for the history of volcanic activity.
Murakami, Hiroaki; Nishiyama, Nariaki; Takeuchi, Ryuji; Iwatsuki, Teruki
Oyo Chishitsu, 64(2), p.60 - 69, 2023/06
In order to confirm the quality control items for borehole closure in radioactive waste disposal projects, in-situ borehole sealing tests using bentonite material were conducted. As a result, the closure performance was successfully demonstrated by comparing the data of water injection tests conducted before and after the installation of the closure material. However, the breakthrough was observed after closing, probably due to high differential pressure applied to the seal section. Thus, it is important to ascertain throughout the entire operation that the borehole is adequately closed. The placement and specifications of the closure material should be determined according to the hydrogeological structure in the borehole. The confirmation items to use bentonite for sealing material are identified to be: to consider swelling and density loss in the borehole; to place the planned depth using appropriate emplacement technique; to be placed without damage to seals when use some backfilling materials, considering effect of permeability on adjacent seals.
Tateishi, Ryo*; Shimada, Koji; Shimizu, Mayuko; Ueki, Tadamasa*; Niwa, Masakazu; Sueoka, Shigeru; Ishimaru, Tsuneari
Oyo Chishitsu, 62(2), p.104 - 112, 2021/06
We attempted to discriminate between active and non-active faults by linear discriminant analysis using the chemical composition data of fault gouges in Japan, and then examined the elements that represent the difference between them and better discriminants. As a result, the multiple discriminants obtained could discriminate between them with high probability. In addition, the generalization performance of these discriminants is discussed, and the discriminants that can be expected to have high discriminant performance for unknown samples are presented. Also, from the combination of elements common to these discriminants, we narrowed down the number of elements that represent the difference between active and non-active faults to 6, and showed that the combination of TiO and Sr contributing the most to the discrimination. The method applied in this study is an innovative one that can discriminate the activity by chemical analysis of fault rocks that are universally present in the bedrock.
Aoki, Kazuhiro; Tanaka, Yukumo; Yoshida, Takumi; Shimada, Koji; Sakai, Toru*; Kametaka, Masao*; Seshimo, Kazuyoshi
Oyo Chishitsu, 62(2), p.64 - 81, 2021/06
Co-seismic surface ruptures in the Fukushima-ken Hamadori Earthquake of Mw 6.7 on April 11, 2011 exposed approximately 14 km trending NNW-SSE from Nameishi to northwest of Ishizumi Tsunaki of Tabito Town, Iwaki City and were newly named the Shionohira Fault. However, no surface ruptures appeared along an N-S trending active Kuruma fault extending 5 km south of the Shionohira Fault. Because of the proximity and similar strike, two locations in Shionohira Fault and one location in Kuruma fault were selected as the study area for the fault activity evaluation. The present study reports the results of a series of geological and drilling surveys, core observation, XRD, isotope, and fluid inclusion analyses, and water permeability test. The results obtained from the three locations offer a fundamental data base that can be utilized for fault activity evaluation by summarizing the geological, mineralogical, and fluid property characteristics of fault fracture zone.
Yonaga, Yusuke; Sano, Naomi*; Amamiya, Hiroki*; Ogita, Yasuhiro; Niwa, Masakazu; Yasue, Kenichi*
Oyo Chishitsu, 62(1), p.2 - 12, 2021/04
Provenance analysis based on quick identification of heavy minerals using an electron probe microanalyzer (EPMA) was applied to samples from Pleistocene sediments in Horonobe region, Hokkaido, where major provenance rocks can be sedimentary and mafic igneous rocks. The concentrations of 16 elements were measured in individual grains to identify the mineral species based on their chemical composition. In addition, microscopic observation of thin sections and gravel composition analysis were conducted to confirm the validity of the quick identification of heavy minerals. These analyses clarify that combinations of several heavy mineral species can be a useful index of provenance rocks from the Soya Hill and Teshio Mountains, and suggest that uplift of the Soya Hill after ca. 1.5 Ma constrained supply of sediments from the Teshio Mountains. On the other hand, minerals uncommon both in the Soya Hill and Teshio Mountains, such as hornblende, are included in the Pleistocene sediments. This suggests that a sediment supply from distant area was also significant, like transportation by the Teshio River. The method for quick identification of heavy minerals using EPMA can provide an information about provenance rocks difficult to identify only by gravel composition analysis.
Murakami, Hiroaki; Ashizawa, Masaomi*; Tanaka, Kazuhiro*
Oyo Chishitsu, 59(1), p.2 - 12, 2018/04
This study describes the features of fractures and their fillings along with the long-term behavior of their hydrogeological structures in an underground environment based on the results of a geological investigation conducted at an underground facility in northern Kyushu. Fractures were classified into five groups on the basis of fracture orientation: A, B, C, D, and low-angle groups. The genesis of all fractures is the cooling process of granodiorite pluton. Almost all of the water-conducting fractures are included in the B group. Because a number of fracture fillings in the B group are filled by prehnite and crushed fragments of epidote and quartz, the fractures in this group alternated sealing and re-opening. The fracture characteristics in the B group are follow as: accompanying many alteration halos, long trace length, and cutting off other fractures. These results indicate that fractures in the B group have possibly functioned as pathways for groundwater flow in the long term.
Tanaka, Yoshihiro*; Kametaka, Masao*; Okazaki, Kazuhiko*; Suzuki, Kazushige*; Seshimo, Kazuyoshi; Aoki, Kazuhiro; Shimada, Koji; Watanabe, Takahiro; Nakayama, Kazuhiko
Oyo Chishitsu, 59(1), p.13 - 27, 2018/04
This paper aims to develop a methodology for understanding the fault activity by observing exposed fault planes without covering younger strata. Based on purpose, faults developed in relatively homogeneous rocks such granitic types are investigated as follows; Gosuke Dam upstream outcrop of Gosukebashi Fault and Funasaka-nishi outcrop of Rokkou Fault were selected for the study of an active fault; and K-3 outcrop of Rokkou Houraikyo Fault was chosen for a non-active fault.
Mizuno, Takashi; Iwatsuki, Teruki; Matsuzaki, Tatsuji*
Oyo Chishitsu, 58(3), p.178 - 187, 2017/08
no abstracts in English
Ishibashi, Masayuki; Yuguchi, Takashi*
Oyo Chishitsu, 58(2), p.80 - 93, 2017/06
Mode of granitic rocks is important information for evaluating their formation process, characterizing fracture distribution and understanding mass transfer in the rock matrix. However, previous methods to evaluate the mode of granitic rocks have several issues. Thus, this study provides the new image analysis method (MJPD method) using scanning X-ray analytical microscope for evaluation of mineral distribution and mode including the secondary minerals. The MJPD method can deal with the heterogeneity of elemental distribution in each mineral. For evaluating the applicability of MJPD method, the method was applied to elemental maps of thin sections. As a result, it was found out that the mineral distribution and mode are easily evaluated by MJPD method using the elemental maps measured in approximately 10,000 seconds. In addition, the MJPD method can be potentially applied to the elemental maps obtained by other analytical instrumentation such as EPMA and SEM-EDS.
Masumoto, Kazuhiko*; Takeuchi, Ryuji
Oyo Chishitsu, 57(4), p.154 - 161, 2016/10
Fractures developing around the tunnel during the excavation result in issues related not only to the mechanical stability of the rock cavern, but also to the groundwater flow paths. In order to estimate the possibility of application of the GPR (Ground Penetration Radar) to estimate the fractures as low paths, the authors conducted the GPR survey along the side wall of 500 m access tunnel of the Mizunami Underground Research Laboratory of JAEA. The results of the profile measurements indicated that water-conductiong fractures were detected as a reflected waves using GPR survay. Furthermore, as the results of fixed-point measurements during the injection of the saline water, it could be indicated to estimate the flow paths of saline water in the fractures, in a non-destructive way, based on spectral analysis in the reflected waveforms of GPR.
Tsuruta, Tadahiko; Sasao, Eiji
Oyo Chishitsu, 56(6), p.298 - 307, 2016/02
Japan Atomic Agency (JAEA) are performing Mizunami Underground Research Laboratory project (MIU project), which is a broad scientific study of the deep geological environment as a basis of research and development for geological disposal of nuclear wastes. Geological investigations, reflection seismic surveys, borehole drilling, etc., are carried out to understand the distribution and properties of important geological structures (permeable fractures, faults, etc). This report summarizes specifications and data characteristic of geological mapping on the shafts and gallery wall, and describes contributions to developments of geological model based on the results of geological mapping.
Ishii, Eiichi; Matsuoka, Toshiyuki; Saegusa, Hiromitsu; Takeuchi, Ryuji
Nihon Oyo Chishitsu Gakkai Heisei-27-Nendo Kenkyu Happyokai Koen Rombunshu, p.135 - 136, 2015/09
no abstracts in English
Oyo Chishitsu, 55(5), p.216 - 228, 2014/12
Regarding grouting of geological disposal repository, geological research that shows the site specific existent condition and aggregation form of rock fractures reached ca.1000 m underground, which buried high-level radioactive waste, is necessary, by a limited number of rock boring survey in the earlier stage of the site investigation. And this fundamental problem holds the key to the success and failure of modeling, design and construction of grouting. This paper introduces rock fractures boring column by simulant real boring core, and attempted to overview of fractures perspective intervening and outer space of borings based on the cross-sectional representation of fractures. Using fractures column, each fracture's location, orientation, and those morphological combination forming fractures aggregate zone are shown systematically. In addition, the relationships between rock fractures and geological features, rock grading are shown in parallel.
Ishibashi, Masayuki; Ando, Tomomi*; Sasao, Eiji; Yuguchi, Takashi; Nishimoto, Shoji*; Yoshida, Hidekazu*
Oyo Chishitsu, 55(4), p.156 - 165, 2014/10
Understanding of long-term history of water-conducting features such as flow-path fractures is key issue to evaluate deep geological environment for geological disposal of high-level radioactive waste (HLW). Thus, we conducted study on the geological features and the long-term behavior of flow-path fractures based on the data obtained at -300m levels in the Mizunami Underground research laboratory (MIU), central Japan. Total 1670 fractures were mapped in underground gallery at the -300m levels. Flow-path fractures occupy about 11% of all fractures. The flow-path fractures are divided into grout filling fractures and low inflow-rate fractures. All of the grout filling fractures is filled with calcite as fracture filling minerals without conspicuous host rock alteration around fractures. The low inflow-rate fractures possessed similar geological character with the sealed fractures which are not acted as flow-path. The geological character of fracture filling and host tock alteration around fractures indicates the history of the formation at the time of intrusion and emplacement of host granite (Stage I), then filling at hydrothermal event (Stage II), and finally opening and elongation during exhumation stage (Stage III). In conclusion, the present flow-path fractures were formed by opening and/or elongation of pre-existed fractures, which were filled at the hydrothermal event, at the time of exhumation.
Nohara, Shintaro*; Nakata, Eiji*; Suenaga, Hiroshi*; Tanaka, Shiro*; Kubota, Kenji*; Oyama, Takahiro*; Kondo, Keiji
Nihon Oyo Chishitsu Gakkai Heisei-25-Nendo Kenkyu Happyokai Koen Rombunshu, p.129 - 130, 2013/10
no abstracts in English
Sanada, Yukihisa; Torii, Tatsuo
"Higashi Nihon Daishinsaigo No Oyo Chishitsugaku, Aratana Kadai Toshiteno Haikibutsu Shori To Hoshano Osen" Yokoshu, p.28 - 36, 2013/06
The airborne radiation monitoring technique is developing rapidly by the improvement of the pinpointing technology such as the GPS and the spread of GIS technologies. In addition, a technique to measure the wide area in a short time is demanded. Here, we speak the development of the aiborne radiation measurement technology that JAEA performs since a Fukushima Dai-ichi Nuclear Power Plant accident.
Furusawa, Akira*; Yasue, Kenichi; Nakamura, Chisato*; Umeda, Koji
Oyo Chishitsu, 54(1), p.25 - 38, 2013/04
Distinguishing strongly weathered tephras is very difficult because major-element chemistry of volcanic glasses is affected by weathering. On the other hand, it recently became clear that major-element analysis of glass inclusions in quartz and plagioclase is an effective method of investigating strongly weathered tephras. We studied the weathered tephras in the Toki Sand and Gravel Formation (TSG) located on the Nenoue highland, in the hanging wall of the Byobuyama fault. The TSG consists mainly of gravel beds with intercalated clay-sand beds in the lower and middle horizons. Glass inclusions in the quartz occur only in the weathered clay-sand beds. We found that the glass inclusions in the quartz in the middle horizons of the TSG provide the best correlations with those in the Minamidani-1 tephra deposits in the Kinki, Chubu and Shin-etsu Districts.
Kawamura, Makoto; Ebashi, Takeshi; Makino, Hitoshi; Niizato, Tadafumi; Yasue, Kenichi; Inagaki, Manabu; Oi, Takao
Oyo Chishitsu, 51(5), p.229 - 240, 2010/12
Uplift, subsidence, denudation, and sedimentation are phenomena over long-term in a regional scale. It is difficult to ignore the impacts of those phenomena on a disposal system completely in long-term. Therefore, type and extent of the impacts on geological and disposal environmental conditions, and disposal systems need to be evaluated quantitatively in order to develop perturbation scenarios. We have been developing a systematic methodology to develop perturbation scenarios based on the appropriate understanding of those phenomena. The variety of the change of geological environment and evolution pattern of the environment, which are caused by the variation of the uplift, subsidence, denudation, sedimentation phenomena and those rates, are understood by arranging the information in the framework of the thermal-hydrological-mechanical-chemical-geometrical (T-H-M-C-G) system, and the impacts of those environmental change to the performance of the repository system are also examined by using the T-H-M-C-G system. In this study, firstly, the potential changes of the geological environment were identified by examination of possible combinations of the uplift/denudation and subsidence/ sedimentation. The effects of the initial environmental condition are also considered. Geohistorical information and View of Modern analogue theory should be used in this stage. This procedure is essential to set up the scenarios regarding uplift/denudation and subsidence/sedimentation, to clarify the trend and/or range of the change of the geological environmental conditions. Then, the phenomena which give the large impacts to a disposal system were extracted based on the T-H-M-C-G system. By applying the developed framework which deals with the impacts on the HLW disposal system realistic view and builds evaluation scenarios and models based on step wise manner, we acquired the prospect that realistic uplift and denudation scenario could be built to this examination procedure.
Tagami, Masahiko; Ishida, Hideaki; Tsuruta, Tadahiko
Nihon Oyo Chishitsu Gakkai Heisei-21-Nendo Kenkyu Happyokai Koen Rombunshu, p.175 - 176, 2009/10
Fractures in crystalline rocks have exerted a big influence on the underground water stream. It is necessary to understand the fracture shape and distribution from the viewpoint of the material transfer and the safety construction in designing the geological disposal facilities of the high-level nuclear waste. In this report, we examined the fracture characteristics along the horizontal tunnel which was named -300m Access/Research gallery in Mizunami Underground Research Laboratory. Spring water that exceeded 1000 liters per minute was confirmed in the horizontal boring investigation along the tunnel before gallery excavation. We considered the fracture formation process and the function as the passage of water.
Funaki, Hironori; Ishii, Eiichi; Tokiwa, Tetsuya
Oyo Chishitsu, 50(4), p.238 - 247, 2009/10
Evaluation of the role of fracture as the major water-conducting feature in sedimentary rocks is indispensable information to carry out the modelling and analysis of the groundwater flow. We conduct core logging, acoustic televiewer logging and fluid electric conductivity logging at a borehole to clarify the relationship between fracture and flow point. As a result, most of the fractures in the Koetoi Formation don't have a function as major water-conducting features, but some of the fractures in the Wakkanai Formation do. The further statistical analysis indicates; (1) fracture interconnectivity in the Koetoi Formation is poor, while that in the Wakkanai Formation exists to some extent, (2) fracture aperture in the Wakkanai Formation tends to be more than that in the Koetoi Formation. These suggest that the Koetoi Formation would be porous medium and the Wakkanai Formation would be stronger in property as fractured medium than the Koetoi Formation.