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Takayama, Yusuke; Tachibana, Shinya*; Iizuka, Atsushi*; Kawai, Katsuyuki*; Kobayashi, Ichizo*
Soils and Foundations, 57(1), p.80 - 91, 2017/02
Times Cited Count:11 Percentile:48.47(Engineering, Geological)Bentonite has remarkable swelling characteristics and low permeability that makes it a suitable buffer material in a purpose built repository for the geological disposal of radioactive waste. It is necessary to use reliable numerical simulation techniques to demonstrate that the repository is safe and mechanically stable for tens of thousands of years. Constitutive model that describes the mechanical behavior of bentonite is a key technique in such numerical simulations. The current paper proposes a constitutive model for bentonite, which treats bentonite as an unsaturated elasto-plastic material that changes its mechanical properties as it becomes saturated. In the proposed model, the swelling index and an expression formula for negative dilatancy are treated as functions of degree-of-saturation. Montmorillonite content is used as an input parameter in the proposed model and so is applicable to a variety of bentonite based materials of varying montmorillonite content. Experimental results from swelling volume and swelling pressure tests taken from the literature are shown to be satisfactorily predicted by the proposed model.
Toida, Masaru*; Suyama, Yasuhiro*; Mori, Takayuki*; Inaba, Takeshi*; Atsumi, Hiroyuki*; Tanaka, Toshiyuki*; Kobayashi, Ichizo*; Nakajima, Makoto*; Ogata, Nobuhisa
JAEA-Research 2007-071, 159 Pages, 2007/09
"Geoscientific research" at the Tono Area is developing site investigation, characterization and assessment techniques for understanding of geological environment. Their important goal is to establish a methodology for analyzing uncertainties in a heterogeneous geological environment and to develop investigation techniques for efficiently reducing the uncertainties. In Fiscal Year 17, in addition to information from the MIZ-1 borehole investigation, present knowledge has been compiled. The proposed technique has been improved through conceptual geological modeling and groundwater analyses at the Tono Area. Design options for handling geological uncertainties based on the characterization of the geological environment have also been tested. The results of this study can be summarized as follows: (1) It was shown that the fracture group with NW strike has high correlation with maximum measured transmissivity. This was maybe caused by the effect of regional in situ stress. (2) Through conceptual geological modelling and groundwater analysis, a procedure for modelling of the geological environment with heterogeneous characteristics was proposed. (3) From the viewpoint of improving the design of an underground facility, the existence of uncertainties of the geological environment with heterogeneous characteristics requests multiple options. A design option should be adapted to the geological environment with heterogeneous characteristics.
Toida, Masaru*; Suyama, Yasuhiro*; Mori, Takayuki*; Inaba, Takeshi*; Sasakura, Takeshi*; Atsumi, Hiroyuki*; Masumoto, Kazuhiko*; Kobayashi, Ichizo*; Iwano, Keita*; Furuichi, Mitsuaki*; et al.
JAEA-Research 2007-065, 210 Pages, 2007/09
"Geoscientific research" at the Tono Area is developing site investigation, characterization and assessment techniques for understanding of geological environment. Their important goals are to establish a methodology for analyzing uncertainties in heterogeneous geological environment and to develop investigation techniques for efficiently reducing the uncertainties. The current study proposes a new approach where all the possible options in the models and data-sets, which cannot be excluded in the light of the evidences available, are identified. This approach enables uncertainties associated with the understanding at a given stage of the site characterization to be made explicitly using an uncertainty analysis technique based on Fuzzy geostatistics. This approach supports the design of the following investigation stage and reduces the uncertainties efficiently. In FY H16 the technique has been tested through geological modelling and groundwater analyses with Tono Area case based on current knowledge, to demonstrate its applicability and to compile the knowledge / information required to describe the H17 report. This report can be summarized as follows: (1) The knowledge / information required to describe the heterogeneous characteristics was compiled and connected to uncertainties associated with the characterization of a geological environment using a synthesis diagram. (2) Methodologies for assignment and screening of parameters were developed by using Evidential Support Logic (ESL). (3) Applicability of the techniques could be confirmed with Tono Area case. (4) This report proposed a new methodology that integrates the technique into JAEA ordinary technique to good advantage in the geoscientific research project.
Mihara, Morihiro; Kobayashi, Ichizo*
JAEA-Research 2007-020, 45 Pages, 2007/03
In this study, the dependencies of hydraulic conductivity of the compacted bentonite of which a dry density was 1.8 Mg/m on sodium nitrate concentration were investigated experimentally. The enhancement of hydraulic conductivity was observed using sodium nitrate solution of high concentration. The enhancement of 02mol/L of the nitrate concentration was significant high. In the solution of 2mol/L nitrate, the hydraulic conductivities were hardly changed. The hydraulic conductivities using the sodium nitrate solution of high concentration, 2mol/L, were less than 10m/s which was required value in the repository to restrict the ground water flow. It was more difficult that nitrate concentration of solution affects hydraulic conductivity of the highly compacted bentonite comparing with the lower compacted density bentonite. It was found that the effects of the viscosities of nitrate solution were small.
Seno, Shoji*; Toida, Masaru*; Kobayashi, Ichizo*; Tanaka, Mayumi*; Matsui, Hiroya; Kunimaru, Takanori; Kurikami, Hiroshi
Nihon Chikasui Gakkai 2006-Nen Shuki Koenkai Koen Yoshi, p.310 - 315, 2006/10
no abstracts in English
Toida, Masaru*; Sasakura, Takeshi*; Yokozeki, Kosuke*; Kobayashi, Ichizo*; Watanabe, Kenzo*; Ashizawa, Ryoichi*
JNC TJ8400 2004-036, 310 Pages, 2005/03
To integrate the system for evaluation of long-term hydraulic condition in near field of TRU waste disposal, the engineered barrier, which consists of bentonite buffer and cementitious materials, was employed in the series of laboratory tests. On the bentonite buffer, with the aim of investigating of the effect of (i)interlayer cation in bentonite, (ii)content of siliceous sand and (iii)the ionic strength of ground water on its mechanical and hydraulic properties, series of laboratory tests were conducted. The same lot of bentonite was used in the series of tests to obtain consistent data. In addition, the swelling test of the laminated bentonite with caliumization front was conducted for verification of the proposed constitutive model. On cementitious materials, the altered specimen that produced immersing was investigated the water permeation and also characteristics. The hardened cement paste specimens with W/C=40 to 105% were immersed into deionized water and alteration behavior under diffusion condition was investigated.
Toida, Masaru*; Sasakura, Takeshi*; Atsumi, Hiroyuki*; Masumoto, Kazuhiko*; Tanaka, Toshiyuki*; Suyama, Yasuhiro*; Kobayashi, Ichizo*
JNC TJ8400 2004-023, 146 Pages, 2005/02
To establish sealing technique suitable for geological environmental conditions of Japan, it is necessary to obtain data related with this sealing function through laboratory tests and in-situ tests. It also is necessary to put these data to practical use and to establish the estimating method of the sealing technique.Tunnel sealing experiment, which has been carried out as collaboration between JNC and AECL at URL of AECL Canada, is progressing in the final stage and fundamental data relating with the sealing function has almost obtained. This report deals with the total data processing and interpretation of the sealing experiment, as well as the numerical analysis and interpretation on tracer test results. Conceptual plans of the experiment to confirm the performance of tunnel sealing technique in a sedimentary rock are also discussed.
Toida, Masaru*; Sasakura, Takeshi*; Atsumi, Hiroyuki*; Suyama, Yasuhiro*; Kobayashi, Ichizo*; Kawabata, Junichi*; Ito, Keijiro*
JNC TJ8400 2003-088, 254 Pages, 2004/02
To establish sealing technique suitable for geological environmental conditions of Japan, it is necessary to obtain data related with this sealing function through laboratory tests and in-situ tests. It also is necessary to put these data to practical use and to establish the estimating method of the sealing technique. Tunnnel sealing experiment, which has been carried out as a joint research between JNC and AECL at URL of AECL Canada, is arriving the final stage and fundamental data relating with the sealing function has almost obtained. This report deals with the total data processing and interpretation of the sealing test, as well as the numerical analysis and interpretation on tracer test results. Concrete plans for the disassembling and sampling of clay and concrete plugs, which is important for the evaluation of function of the sealing system, is also discussed.
Toida, Masaru*; Suyama, Yasuhiro*; Inaba, Takeshi*; Sasakura, Takeshi*; Atsumi, Hiroyuki*; Tanaka, Toshiyuki*; Kobayashi, Ichizo*; Iwano, Keita*; Furuichi, Mitsuaki*
JNC TJ7400 2004-017, 521 Pages, 2004/02
"Geoscientific research" at Tono is developing site investigation, characterization and assessment techniques for understanding of geological environment. Their important themes are to establish a methodology for analyzing uncertainties in heterogeneous geological environment and to develop investigation techniques for reducing the uncertainties efficiently. The current study proposes a new approach where all the possible options in the models and data-sets that cannot be excluded in the light of the evidence available is identified. This approach enables uncertainties associated with the understanding at a given stage of the site characterization to be made explicitly using an uncertainty analysis technique based on Fuzzy geostatistics. This, in turn, supports the design of the following investigation stage to reduce the uncertainties efficiently. In this report the technique has been tested through geological modelling and groundwater analysis with Tono area case based on current knouledge, to demonstrate its applicability. This report summarizes as follows: (1)It is possible to quantify the uncertainties with Tono area case based on current knouledge using the technique. (2)Based on sensitivity analyses, it is possible to support designs of the following investigation stage to reduce the uncertainties efficiently. (3)The methodology of the technique has been developed with Tono area case. (4)The above could evaluate its applicability and propose further issues for synthesis of the methodology.
Sasakura, Takeshi*; Kuroyanagi, Mikio*; Okamoto, Michitaka*; Kobayashi, Ichizo*
JNC TJ8400 2003-048, 180 Pages, 2003/02
Series of laboratory tests were conducted to investigate the effect of 1)cation exchange of Na-bentonite for Ca ion, and 2)the swelling behavior of bentonite, on its mechanical and hydraulic properties.
Sahara, Fumihiro*; Murakami, Takeshi*; Kobayashi, Ichizo*; Mihara, Morihiro; Oi, Takao
no journal, ,
In this paper, the model for the long-term behavior of bentonite-based materials adopted in MACBECE is mainly described.
Mihara, Morihiro; Kobayashi, Ichizo*
no journal, ,
Hydraulic conductivities of highly compacted bentonite with varaetiy of NaNO concentration were obtained.
Shirase, Mitsuyasu*; Ishii, Tomoko*; Kobayashi, Ichizo*; Jo, Mayumi*; Ono, Makoto*; Nakayama, Masashi
no journal, ,
A candidate emplacement concept of the engineered barrier system (EBS) for geological disposal in Japan is vertical emplacement option, which has a certain gap is between the wall of the disposal hole and the buffer material. This gap is considered to be filled with the swollen buffer material (self-sealing function) when the underground water is infiltrated to the buffer material. However, some underground water flow conditions such as a pipe-shaped water channel induce erosion of the buffer material, which causes lowering of the function of the EBS. Therefore, RWMC (Radioactive Waste Management Funding and Research Center) studies engineering countermeasures against piping and erosion. RWMC used an intentional water supply system to test the pre-hydration of bentonite buffers.