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Ijiri, Yuji*; Saegusa, Hiromitsu; Sawada, Atsushi; Ono, Makoto*; Watanabe, Kunio*; Karasaki, Kenji*; Doughty, C.*; Shimo, Michito*; Fumimura, Kenichi*
Journal of Contaminant Hydrology, 103(3-4), p.168 - 181, 2009/01
Times Cited Count：9 Percentile：30.08(Environmental Sciences)Qualitative evaluation of the effects of uncertainties originating from scenario development, conceptual models, and parameter values is an important subject in the area of safety assessment for high-level nuclear waste disposal. In this study, regional-scale groundwater flow analyses for the Tono area, Japan were conducted using three continuous models which were designed to handle heterogeneous porous media. We evaluated the simulation results to quantitatively analyze uncertainties originating from conceptual models. We found that uncertainties originating from conceptual models (1) greatly depend on boundary conditions and hydrological structures to be modeled, which are assigned by modelers, and (2) are larger than uncertainties originating from the variance in realizations of the Monte Carlo method in stochastic modeling.
Saegusa, Hiromitsu; Shimo, Michito*; Fumimura, Kenichi*; Takeuchi, Shinji; Onoe, Hironori
Nihon Chikasui Gakkai 2006-Nen Shuki Koenkai Koen Yoshi, p.258 - 263, 2006/00
no abstracts in English
Shimo, Michito*; Fumimura, Kenichi*; Obara, Yuzo*; Sato, Akira*; Sugawara, Katsuhiko*
JNC TJ8400 2003-091, 67 Pages, 2004/01
JNC-TJ8400-2003-091.pdf:2.72MB
In this year, the method proposed in H14 study was applied to a natural rock fracture in a 10 cm block, which has been prepared for permeability and tracer tests in the future.
Ijiri, Yuji*; Ono, Makoto*; Sugihara, Yutaka*; Shimo, Michito*; Yamamoto, Hajime*; Fumimura, Kenichi*
JNC TJ7400 2004-015, 732 Pages, 2003/10
JNC-TJ7400-2004-015.pdf:34.55MB
In order to establish the most effective procedures for groundwater flow characterization in order to reduce the uncertainty this study, the identidication of essential uncertainty factors for the groundwater flow characterization has been attempted using various conceptual model. In this study, an integrated data flow on the groundwater flow simuration was developed for previously applied various conceptural models. The data flow consists of five steps in order: (1) field investigation, (2) raw / conditioned data, (3) interpretation / data set, (4) conceptualization / modeling / simulation, and (5) results / applications. These are uncertainties in each work and assumption in every step, and the uncertainties have an influence on the modeling methods and simulation resuls. Following the data flow, the uncertain factors affecting the groundwater flow simulation were extracted based on the simulation resuls. Investigation data, methods of investigation and modeling, and analysis technique were examined to solve the problems due to the uncertainties. Acquired information is summarized in the following. As for each work process in the data flow, the uncertainty factors that are considered to affect the results of simulations are extracted by two kinds of comparison methods as follows: (1) comparison of data flow among analysis cases for each conceptual model, and (2) comparison of data flow among conceptual models for each case. The uncertainty factors include hydrogeological mechanism of fault and effective porosity, and the likes. The development of each data flow for four modeling methods was additionally used to clarify the data interpretation technique, the modeling procedure, and the uncertainty factor in each data flow along with the data flow from investigation through evaluation. Extensive through information without bias is, therefore, reflected in groundwater flow analysis by defining the data flow. Establishment of data flow...
Ijiri, Yuji*; Ono, Makoto*; Sugihara, Yutaka*; Shimo, Michito*; Yamamoto, Hajime*; Fumimura, Kenichi*
JNC TJ7400 2004-005, 415 Pages, 2003/03
JNC-TJ7400-2004-005.pdf:23.86MB
For the purpose of evaluating how uncertainties included in modeling of hydrogeological structure and results of groundwater simulation decreased with progress of investigation research, updating and calibration of the models about several modeling techniques of hydrogeological structure and groundwater flow analysis techniques were carried out, based on the information and knowledge which were newly acquired. The acquired knowledge is as follows.The model calibration is performed by the method of matching numericals simulation with observation, about the pressure response caused by opening and closing of a packer in MIU-2 borehole. Each analysis technique attains reducing of residual sum of squares of observations and results of numerical simulation by adjusting hydrogeological parameters. However, each model adjusts different parameters as water conductivity, effective porosity, specific storage, and anisotropy. When calibrating models, sometimes it is impossible to explain the phenomena only by adjusting parameters. In such case, another investigation may be required to clarify details of hydrogeological structure more.Since it is a little more flexible about boundary condition and faults except Tsukiyoshi fault than last year, travel paths themselves vary a little rather than last year. However, as a result, when travel paths are almost the same, model calibration can reduce the variation of travel length and Darcy velocity among models within about one order. It will be necessary to propose investigation aiming at reducing the uncertainty of data, such as water conductivity and effective porosity and at making hydrogeological structure more detailed from a viewpoint of modeling.
Ijiri, Yuji*; Ono, Makoto*; Sugihara, Yutaka*; Shimo, Michito*; Yamamoto, Hajime*; Fumimura, Kenichi*
JNC TJ7400 2004-003, 610 Pages, 2003/03
JNC-TJ7400-2004-003.pdf:42.03MB
This study involves evaluation of uncertainty in hydrogeological modeling and groundwater flow analysis. Three-dimensional groundwater flow analisys in underground research laboratory site in Tono was carried out using three continuum models and one discontinuum model in the domain of 9km
9km area. The acquired knowledge is as follows.The effect of variety of modeling method was evaluated under the condition that same analysis domain and same shape of Tsukiyoshi fault were assingned. The results indicated that the variation of travel pathway and travel length resulted from heterogeneity is sometimes larger than from the difference of models, depending on a place. Besides, since the difference between the models in travel time was larger than a travel pathway and travel length, it turns out that the uncertainty of effective porosity used for alculation of the actual flow velocity is large.Moreover, the existing data flow was reconstituted through a series of modeling and analysis of this work. The results indicated that it is necessary to continue reflecting the results of investigation and evaluation in data flow, since data flow varied with modeling concepts.
Shimo, Michito*; Fumimura, Kenichi*; Obara, Yuzo*; Sato, Akira*; Sugawara, Katsuhiko*
JNC TJ8400 2003-021, 82 Pages, 2003/02
JNC-TJ8400-2003-021.pdf:3.05MB
Understanding the influence of small scale structure and its heterogeneity onto flow through rock fractures is important for improving the reliability of performance assessment of Geologic Disposal of High Level Nuclear Waste. An established technique for measuring the fracture aperture profile is required to achieve the above purpose. There are several aperture measuring techniques: (1) estimation of aperture from roughness measurement results, (2) direct measurement of the fracture from rock surface, (3) non-destructive method, such as tomography. Among above, tomography method, which is rather new technique and its applicability to aperture measurement is not well known, is expected to become an effective and feasible approach since the aperture profile can be obtained without destroying the rock specimen. In this work, we investigated problems associated with fracture aperture measurement using X-Ray, then we proposed several approaches to improve measurement accuracy, finally
Shimo, Michito*; Yamamoto, Hajime*; Jo, Mayumi*; Yamagami, Masahito*; Fumimura, Kenichi*; Kumamoto, So*; Igarashi, Takafumi*
JNC TJ7440 2005-083, 991 Pages, 2003/01
JNC-TJ7440-2005-083.PDF:130.74MB
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