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2013 Volume 52 Issue 1 Pages
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Published: August 19, 2013
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
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Article type: Index
2013 Volume 52 Issue 1 Pages
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2013 Volume 52 Issue 1 Pages
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2013 Volume 52 Issue 1 Pages
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
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Published: August 19, 2013
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Motohei KANAYAMA, Masataka AKASHI, Akiko NAKANO, Masami OHTSUBO, Takah ...
Article type: Article
2013 Volume 52 Issue 1 Pages
1-8
Published: August 19, 2013
Released on J-STAGE: June 22, 2017
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There is a growing concern socially for the recycling of wastes, and in the geotechnical engineering community ground improvement by reusing wastes is expected to be developed. In the present study, laboratory tests have been conducted to examine the cementation of soil due to carbonate production in the presence of oyster shell with expected metabolic activity of microorganisms. Toyoura standard sand and marine clay sediment were used as soil samples. The soil samples were mixed with buffer solution and the oyster shell in test tubes, and were shaken for 24 hours, and then commercial yeast and glucose were added to the soil samples. Changes in the calcium ion concentration and pH with time for the prepared soil suspension were recorded and how the soil samples were solidified was visually observed. The calcium concentration in the solution decreased rapidly and reached a constant value after 12 hours, which indicates that the calcium in the liquid phase of the soil samples was precipitated as carbonate. Similar treatment for soil cementation was given to the paste of the standard sand and the marine clay; the specimen of the sand and marine clay cured for 5 days gained the strength of about 14 and 9 times higher, respectively, compared with the specimen cured for 0 days. These results indicate that the cementation using waste oyster shell has the potential of being used for ground improvement when considering waste recycling.
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Ryo NAKABAYASHI, Tatsuya KIJIMA, Yasumoto TSUKADA, Tsutomu SATO, Tsuba ...
Article type: Article
2013 Volume 52 Issue 1 Pages
9-22
Published: August 19, 2013
Released on J-STAGE: June 22, 2017
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Dissolution rates of montmorillonite in bentonite under hyperalkaline conditions have been obtained to evaluate the long-term performance of engineered barriers for radioactive waste disposal. The saturation state of pore water with respect to montmorillonite in bentonite has been demonstrated as an important factor controlling montmorillonite dissolution rate. Pore water chemistry including the saturation state may be significantly affected by the dissolution of accessory minerals in bentonite. The bentonite "Kunigel V1", which is being considered for use in radioactive disposal barriers in Japan, actually contains a large amount (〜50 %) of accessory silica minerals, such as chalcedony and quartz. Dissolution of the silica minerals may inhibit the dissolution of montmorillonite in the bentonite by increasing the silica concentration and hence the saturation state with respect to montmorillonite in the pore water. Therefore, the objectives of this study are to examine the dissolution kinetics of the silica minerals and the effect of dissolved silica on the dissolution of montmorillonite in a compacted bentonite using X-ray computed tomography (CT) and geochemical modeling. Advective alteration experiments of a compacted bentonite (Kunigel V1) with a dry density of 0.3 Mg/m^3 was conducted with 0.3M NaOH solution at 70℃ for 360 days. X-ray CT images, which were taken every 10 days, showed that the volume of a light colored material decreased as the interaction between the bentonite and hyperalkaline-fluid progressed during the experiments. This is attributed to the dissolution of accessory silica minerals in the bentonite. XRD analyses of altered bentonite after the experiments identified that the accessory mineral was mainly chalcedony. The kinetic data for dissolution of chalcedony was obtained by developing the methodology to quantify the volume of accessory minerals in the CT images. These results showed that chalcedony was almost completely dissolved in the area close to the fluid input within 80 days. The geochemical transport model consistent with the experimental results indicates that the pore water in the bentonite became near saturation with respect to montmorillonite due to the dissolution of silica minerals in bentonite, inhibiting the dissolution of montmorillonite in bentonite. The model also indicates that the inhibition of montmorillonite dissolution will not be sustained beyond the experimental duration under the same experimental conditions. However, a compacted bentonite with higher dry density such as 1.6 Mg/m^3, where diffusion is the dominant mass transport mechanism, has been considered for use in actual radioactive disposal barriers in Japan. In the much more compacted bentonite system, dissolution of montmorillonite will be inhibited for a much longer term. Therefore, it is important to consider the dissolution behavior of silica minerals to sufficiently evaluate the long-term performance of bentonite as a component of engineered barriers for radioactive waste disposal.
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Masaharu NAKAGAWA
Article type: Article
2013 Volume 52 Issue 1 Pages
23-31
Published: August 19, 2013
Released on J-STAGE: June 22, 2017
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The Besshi copper mine in Niihama City, central Shikoku, produced 700,000 tons of copper from 1691 to 1973, contributing to Japan's economic development and supporting the prosperity of the Sumitomo Group and Niihama City. A unique industrial heritage with many historical buildings remains in the Besshi area. Many bedded cupriferous iron sulfide deposits occur closely associated with basic schist in the Cretaceous Sanbagawa high-P/T metamorphic belt. The Sanbagawa belt was an accretionary complex derived from oceanic crust with pelagic sediments and trench turbidites. The Besshi deposit is the largest cupriferous deposit in Japan, and the tabular ore body of the massive sulfide ore occurs between basic schist and quartz schist. The ore consists mainly of pyrite and chalcopyrite with accessories of sphalerite and bornite. The Besshi sulfide deposit is considered to have been the hydrothermal precipitate formed by the mid-oceanic ridge volcanism and have been accreted onto the proto-Japanese Island by underplating at great depth.
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Shingo YOKOYAMA, Hirohisa YAMADA, Yujiro WATANABE, Kotaro NAKATA, Kenj ...
Article type: Article
2013 Volume 52 Issue 1 Pages
32-39
Published: August 19, 2013
Released on J-STAGE: June 22, 2017
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[in Japanese]
Article type: Article
2013 Volume 52 Issue 1 Pages
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Published: August 19, 2013
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
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2013 Volume 52 Issue 1 Pages
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
42-43
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
44-45
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2013 Volume 52 Issue 1 Pages
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
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Published: August 19, 2013
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Article type: Appendix
2013 Volume 52 Issue 1 Pages
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Published: August 19, 2013
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Article type: Cover
2013 Volume 52 Issue 1 Pages
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Published: August 19, 2013
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Article type: Cover
2013 Volume 52 Issue 1 Pages
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