Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 27

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Joint clarification of contaminant plume and hydraulic transmissivity via a geostatistical approach using hydraulic head and contaminant concentration data

Takai, Shizuka; Shimada, Taro; Takeda, Seiji; Koike, Katsuaki*

Mathematical Geosciences, 56(2), p.333 - 360, 2024/02

 Times Cited Count:0 Percentile:0.00(Geosciences, Multidisciplinary)

To enable proper remediation of accidental groundwater contamination, the contaminant plume evolution needs to be accurately estimated. In the estimation, uncertainties in both the contaminant source and hydrogeological structure should be considered, especially the temporal release history and hydraulic transmissivity. Although the release history can be estimated using geostatistical approaches, previous studies use the deterministic hydraulic property field. Geostatistical approaches can also effectively estimate an unknown heterogeneous transmissivity field via the joint data use, such as a combination of hydraulic head and tracer data. However, tracer tests implemented over a contaminated area necessarily disturb the in situ condition of the contamination. Conversely, measurements of the transient concentration data over an area are possible and can preserve the conditions. Accordingly, this study develops a geostatistical method for the joint clarification of contaminant plume and transmissivity distributions using both head and contaminant concentration data. The applicability and effectiveness of the proposed method are demonstrated through two numerical experiments assuming a two-dimensional heterogenous confined aquifer. The use of contaminant concentration data is key to accurate estimation of the transmissivity. The accuracy of the proposed method using both head and concentration data was verified achieving a high linear correlation coefficient of 0.97 between the true and estimated concentrations for both experiments, which was 0.67 or more than the results using only the head data. Furthermore, the uncertainty of the contaminant plume evolution was successfully evaluated by considering the uncertainties of both the initial plume and the transmissivity distributions, based on their conditional realizations.

Journal Articles

Evaluating the effectiveness of a geostatistical approach with groundwater flow modeling for three-dimensional estimation of a contaminant plume

Takai, Shizuka; Shimada, Taro; Takeda, Seiji; Koike, Katsuaki*

Journal of Contaminant Hydrology, 251, p.104097_1 - 104097_12, 2022/12

 Times Cited Count:3 Percentile:32.31(Environmental Sciences)

When assessing the risk from an underground environment that is contaminated by radioactive nuclides and hazardous chemicals and planning for remediation, the contaminant plume distribution and the associated uncertainty from measured data should be estimated accurately. While the release history of the contaminant plume may be unknown, the extent of the plume caused by a known source and the associated uncertainty can be calculated inversely from the concentration data using a geostatistical method that accounts for the temporal correlation of its release history and groundwater flow modeling. However, the preceding geostatistical approaches have three drawbacks: (1) no applications of the three-dimensional plume estimation in real situations, (2) no constraints for the estimation of the plume distribution, which can yield negative concentration and large uncertainties, and (3) few applications to actual cases with multiple contaminants. To address these problems, the non-negativity constraint using Gibbs sampling was incorporated into the geostatistical method with groundwater flow modeling for contaminant plume estimation. This method was then tested on groundwater contamination in the Gloucester landfill in Ontario, Canada. The method was applied to three water soluble organic contaminants: 1,4-dioxane, tetrahydrofuran, and diethyl ether. The effectiveness of the proposed method was verified by the general agreement of the calculated plume distributions of the three contaminants with concentration data from 66 points in 1982 (linear correlation coefficient of about 0.7). In particular, the reproduced large spill of organic contaminants of 1,4-dioxane in 1978 was more accurate than the result of preceding minimum relative entropy-based studies. The same peak also appeared in the tetrahydrofuran and diethyl ether distributions approximately within the range of the retardation factor derived from the fraction of organic carbon.

Journal Articles

Estimation of contaminated materials concentration by a geostatistical method with groundwater flow

Takai, Shizuka; Shimada, Taro; Takeda, Seiji; Koike, Katsuaki*

Joho Chishitsu, 32(3), P. 95, 2021/09

We received best presentation award GEOINROUM-2021 for the presentation on "Estimation of contaminated materials concentration by a geostatistical method with groundwater flow". We submit the comments of impression for getting the Award to Geoinformatics.

Journal Articles

Characterizing the permeability of drillhole core samples of Toki granite, central Japan to identify factors influencing rock-matrix permeability

Kubo, Taiki*; Matsuda, Norihiro*; Kashiwaya, Koki*; Koike, Katsuaki*; Ishibashi, Masayuki; Tsuruta, Tadahiko; Matsuoka, Toshiyuki; Sasao, Eiji; Lanyon, G. W.*

Engineering Geology, 259, p.105163_1 - 105163_15, 2019/09

 Times Cited Count:12 Percentile:49.66(Engineering, Geological)

Rock matrix permeability is mainly controlled by microcracks. This study aims to identify the factors influencing the permeability of the Toki granite, central Japan. Permeability of core samples, measured by a gas permeameter, largely increases in the fault and fracture zones. Although a significant correlation is identified between permeability and P-wave velocity, this correlation is enhanced by classifying the samples into two groups by the Mn/Fe concentration ratio. Thus, lithofacies is another control factor for permeability due to the difference in mineral composition. Moreover, permeability shows significant negative and positive correlations with Si and Ca concentrations, respectively. These concentrations are probably affected by dissolution of silicate minerals and calcite generation in the hydrothermal alteration process. Therefore, a combination of hydrothermal alteration and strong faulting are the predominant processes for controlling permeability.

Journal Articles

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

 Times Cited Count:27 Percentile:66.20(Geochemistry & Geophysics)

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.

Journal Articles

3D hydraulic conductivity modeling of fractured granitic body using geostatistical techniques and its application to regional groundwater flow analysis

Kubo, Taiki*; Koike, Katsuaki*; Liu, C.*; Kurihara, Arata*; Matsuoka, Toshiyuki

Chigaku Zasshi, 122(1), p.139 - 158, 2013/03

Numerical simulations have been the most effective method for estimating flow pattern, flux, and flow velocity of the groundwater to precisely characterize large-scale groundwater systems. Spatial modeling of the 3D distribution of hydraulic conductivity over a study area is indispensable to obtain accurate simulation results. However, such spatial modeling is difficult in most cases due to the limitations of hydraulic conductivity data in terms of their volume and location. To overcome these problems and establish an advanced technique, we adopt geostatistics and combine a fracture distribution model with measured conductivity data, selecting the Tono area situated in Gifu Prefecture, central Japan for the field study. The size of the main target area covers 12 km (E-W) by 8 km (N-S), with a depth range of 1.5 km, and it is chiefly underlain by Cretaceous granite. Because the distribution of 395 hydraulic test data acquired along the 25 deep boreholes was biased, the data values were compared to the dimensions of simulated fractures using GEOFRAC. As a result, a positive correlation was identified. Using a regression equation for the correlation, hydraulic conductivity values were assigned to every simulated fracture. Then, a sequential Gaussian simulation (SGS) was applied to construct a 3D spatial model of hydraulic conductivity using those assumed values and actual test data. The plausibility of the resulting model was confirmed through the continuity of high and low permeable zones. The next step is a groundwater flow simulation using MODFLOW and the model. The simulation results were regarded to be appropriate because distribution of hydraulic head, locations of major discharge points, and anisotropy of hydraulic behavior of the Tsukiyoshi fault correspond to the results of observations.

Journal Articles

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

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.

Journal Articles

Applying vegetation indices to detect high water table zones in humid warm-temperate regions using satellite remote sensing

Koide, Kaoru; Koike, Katsuaki*

International Journal of Applied Earth Observation and Geoinformation, 19, p.88 - 103, 2012/10

 Times Cited Count:7 Percentile:26.10(Remote Sensing)

This paper presents a method for detecting high water-table areas based on vegetation information in a humid warm-temperate forest area using remotely sensed data (SPOT). The purpose is to develop methodologies for characterizing hydrogeological structures at a regional scale. To detect differences in vegetation conditions due to groundwater supply, a new vegetation index (AgbNDVI) and a segmentation analysis based on geographical characteristics were proposed. A study area was selected in the Tono region of central Japan. As a result, most of the high-VI points are located on the concave/convex slopes, in the vicinity of geologic boundaries, around groundwater seeps and in high water-table areas. Therefore, high-VI points can be a crucial marker for estimating hydraulic properties of geologic structures and groundwater flow regime. Consequently, the proposed method can be an useful tool to detect high water-table areas in humid warm-temperate forest areas.

Journal Articles

Detecting distribution pattern of latent hydrothermally altered zones by geobotanic remote sensing

Koike, Katsuaki*; Uchiyama, Kyosuke*; Koide, Kaoru

Joho Chishitsu, 23(2), p.68 - 69, 2012/06

Hydrothermally-altered zones frequently collapse in intense rain and are intimately related to genesis of heavy metal mineralization. Therefore it is very important to investigate their distributions from the viewpoints of disaster prevention and mineral resource exploration. This study developed a new vegetation index (VIGS) for detecting abnormalities of vegetation induced by differences in soil chemistry and soil moisture related to hydrothermally-altered zones. The VIGS includes the green and mid-infrared bands, which are highly sensitive to vegetation water stress. To validate its availability, this VI was applied in a landslide prone area (Hachimantai) and a gold deposit area (Hishikari Mine) using Landsat TM data. As a result, it was found that the VIGS is very useful to detect abnormalities of vegetation related with hydrothermally-altered zones because abnormalities of vegetation coincide with landslides and hydrothermally-altered zones associated with gold mineralization.

Journal Articles

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

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.

Journal Articles

Geostatistic analysis for groundwater flow and hydraulic parameters in deep granitic body

Kubo, Taiki*; Koike, Katsuaki*; Kurihara, Arata*; Matsuoka, Toshiyuki

Heisei-23 Nendo (2011 Nen) Shigen, Sozai Gakkai Shuki Taikai Koenshu, p.369 - 370, 2011/09

no abstracts in English

Journal Articles

Identifying groundwater- and slope movement-induced vegetation conditions in a landslide prone area using remotely sensed data

Koide, Kaoru; Koike, Katsuaki*

Proceedings of International Symposium on Earth Science and Technology 2010, p.123 - 128, 2010/12

This paper presents a method for detecting differences in vegetation conditions caused by groundwater seepages and slope movements in a landslide prone area using remotely sensed satellite data. To detect differences in vegetation conditions caused by landslides, a new vegetation index (AgNDVI) and a segmentation analysis based on geographic characteristics was proposed. The study area is located in the northern part of the Hachimantai plateau. The result shows that the high-VI points detected are mainly distributed in the head of the main body below the main scarp and in the outer rim of the landslide toe, and the low-VI points are distributed in the fringe of the main scarp, in the foot of the landslide and along the side boundaries of the main body. Consequently, the high- and low-VI points should be strongly linked to groundwater seepage and slope movement, respectively.

Journal Articles

Characterization and tectonic significance of low-angle fracture distribution in the upper part of a granite body; New insight from the Toki Granite around the Mizunami Underground Research Laboratory (MIU), central Japan

Kurihara, Arata; Amano, Kenji; Liu, C.*; Koike, Katsuaki*

Journal of MMIJ, 124(12), p.710 - 718, 2008/12

The spatial distribution of hydrogeologically-relevant geological structures such as fracture and fault is usually very heterogeneous, varying, in general, according to geological history, scale of observation and rock type. With the objective of improving analytical methods to better understand structural heterogeneities, this paper describes the results of investigations of the spatial relationship between regional geological structures (Tsukiyoshi fault and Tsukiyoshi paleo-channel) and fracture density with special emphasis on low-angle fractures in the Toki granite, central Japan. As a result of the analysis, positive correlations between average of fracture spacing data and the horizontal distances from two regional geological structures have been observed. Because the positive correlations can be approximated with a polynomial function of the response surface, we have obtained an improved understanding of the spatial distribution of low-angle fractures with respect to the location of regional geological structures. We have interpreted that the observed spatial distribution of low-angle fracture density conforms to the tectonic setting, on the assumption that the Tsukiyoshi fault and Tsukiyoshi paleo-channel are probably associated with the pull-apart basin by strike-slip faulting from the past investigations and geophysical surveys for this research area. In addition, the proposed spatial modeling techniques and geological interpretations are able to evaluate certainty of interpreted faults and fractures distributions, quantify general trend in structural heterogeneities and detect unknown faults.

Journal Articles

Construction of Fracture Database System and its Application to Rock Mass Characterization

Noguchi, Yoshifumi*; Iwasaki, Hiroshi*; Kaneko, Katsuhiko*; Koike, Katsuaki*

Joho Chishitsu, 4(2), p.45 - 57, 1993/00

Oral presentation

A Proposed method of multi-scale modeling of fractures and hydraulic properties in geologic media

Koike, Katsuaki*; Liu, C.*; Masoud, A.*; Amano, Kenji; Kurihara, Arata

no journal, , 

no abstracts in English

Oral presentation

Estimation of porewater flow and evolution of porewater chemistry during deposition and consolidation of marine strata using one-dimensional sedimentary basin modeling

Komura, Yuto*; Kashiwaya, Koki*; Miyakawa, Kazuya; Nakata, Kotaro*; Koike, Katsuaki*

no journal, , 

no abstracts in English

Oral presentation

Estimation of fracture density distribution in a granite body based on geological investigation and interpretation; A Case study of data from boreholes around the Mizunami Underground Research Laboratory, central Japan

Kurihara, Arata; Amano, Kenji; Koike, Katsuaki*; Liu, C.*

no journal, , 

The spatial distribution of hydrogeologically-relevant geological structures such as fracture and fault is usually very heterogeneous, varying, in general, according to geological history, scale of observation and rock type. With the objective of improving analytical methods to better understand structural heterogeneities, this paper describes the results of investigations of the spatial relationship between regional geological structures (Tsukiyoshi fault and Tsukiyoshi paleo-channel) and fracture density with special emphasis on low-angle fractures in the Toki granite, central Japan. As a result of the analysis, positive correlations between average of fracture spacing data and the horizontal distances from two regional geological structures have been observed. Because the positive correlations can be approximated with a polynomial function of the response surface, we have obtained an improved understanding of the spatial distribution of low-angle fractures with respect to the location of regional geological structures. We have interpreted that the observed spatial distribution of low-angle fracture density conforms to the tectonic setting, on the assumption that the Tsukiyoshi fault and Tsukiyoshi paleo-channel are probably associated with the pull-apart basin by strike-slip faulting from the past investigations and geophysical surveys for this research area. In addition, the proposed spatial modeling techniques and geological interpretations are able to evaluate certainty of interpreted faults and fractures distributions, quantify general trend in structural heterogeneities and detect unknown faults.

Oral presentation

Spatial modeling of large-scale hydraulic structures in a granite area with consideration on relation to fracture distributions

Kurihara, Arata; Koike, Katsuaki*; Liu, C.*; Masoud, A.*; Amano, Kenji

no journal, , 

In this study, we constructed the spatial model for permeability and water-quality distribution in an analytical area (L = 12 km, W = 8 km, H = 1.5 km), with an existing Multi-scale Modeling method used for geology in Tono area. We recognized that a part of lineaments over 2 km length locate on a boundary between permeability or water-quality divisions from comparing these models with an existing fracture distribution model. Multi-scale Modeling method used for this study can be applied for a method to predict heterogeneous hydraulic structures distribution in rocks.

Oral presentation

Improvement of contaminant plume estimation by a geostatistical method considering groundwater flow and non-negativity

Takai, Shizuka; Shimada, Taro; Takeda, Seiji; Koike, Katsuaki*

no journal, , 

For underground contamination by such as radioactive nuclides and chemicals, the contaminant plume distribution needs to be clarified accurately for effective remedy. However, once a pollutant reaches an aquifer, the transport will be affected by groundwater. In such case, only spatial interpolation of measurement data may be unable to reproduce the contaminant plume. In this study, we considered the estimation method integrated transport information into geostatistical analysis. To gain physically feasible solution, we also considered the non-negativity constraint by Gibbs-sampling. The applicability of the method was confirmed for both hypothetical model and actual contamination case (Gloucester landfill, Canada). As the hypothetical model, we assumed that $$^{3}$$H is leaked for 300 days with 2 peaks. The two peaks of plume could not be reproduced by spatial interpolation (Kriging with a Trend). However, the plume was reproduced well by the geostatistical method with the mean average error (MAE) of 2.8E-9. In the Gloucester landfill, the contamination by 1,4-dioxane in the aquifer (300 $$times$$ 300 $$times$$ 40m$$^{3}$$) was evaluated using 69 points measured in 1982. By the geostatistical method considering groundwater flow and nonnegativity constraint, the large spill in 1978 could be reproduced well compared to previous research by other methods such as minimum relative entropy. The plume was also evaluated well with the MAE of 2.8E-2 mg/L; therefore, the applicability of the method was confirmed.

Oral presentation

Estimation of contaminated materials concentration by a geostatistical method with groundwater flow

Takai, Shizuka; Shimada, Taro; Takeda, Seiji; Koike, Katsuaki*

no journal, , 

For occurrence of underground contamination by such as radioactive nuclides and chemicals, the contaminant plume distribution needs to be clarified accurately for effective remedy. If the pollutant reaches an aquifer, the plume needs to be estimated considering groundwater effect, not only spatial interpolation of measurement data. However, the release history may possibly be unknown or uncertain. In this study, we considered the geostatistical estimation method with groundwater flow. For the hypothetical plume of $$^{3}$$H (2-dimension), in which the measurement error is small and hydrogeological structure is fully known, the unknown release history and contaminant plume was estimated well from a limited number of measurements. We also applied the method to the underground contamination by diphenylarsinic acid (organic arsenical compound) occurred in Kamisu, Ibaraki. The trend of measurement data, which the concentration is high around a well and below the source, agreed with that of estimated plume. The mean absolute error for 32 measurement data was 3.0 mg-As/L. The total release amount of As was estimated as 2.9 kg; however, the total amount calculated by the product of measured concentration and groundwater volume is 40.89 kg. To improve the estimation accuracy, the uncertainty of hydrogeological structure (boundary condition, sorption characteristics etc.) needs to be considered.

27 (Records 1-20 displayed on this page)