Saturated hydraulic conductivity of compacted bentonite–sand mixtures before and after gas migration in artificial seawater
To understand the self-healing property of an engineered barrier for radioactive waste disposal, the hydraulic conductivity of compacted bentonite–sand mixtures saturated with artificial seawater (SW) before and after gas migration was examined. Na- and Ca-bentonites were mixed with fine sand at a r...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2023-01-01
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| Series: | Journal of Rock Mechanics and Geotechnical Engineering |
| Subjects: | |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S1674775522000701 |
| _version_ | 1797950717805199360 |
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| author | Yasutaka Watanabe Shingo Yokoyama Misato Shimbashi Yoichi Yamamoto Takahiro Goto |
| author_facet | Yasutaka Watanabe Shingo Yokoyama Misato Shimbashi Yoichi Yamamoto Takahiro Goto |
| author_sort | Yasutaka Watanabe |
| collection | DOAJ |
| description | To understand the self-healing property of an engineered barrier for radioactive waste disposal, the hydraulic conductivity of compacted bentonite–sand mixtures saturated with artificial seawater (SW) before and after gas migration was examined. Na- and Ca-bentonites were mixed with fine sand at a ratio of 70% bentonite in dry weight. Two aspects were considered during the experiment: the hydraulic conductivity of the specimen that was resaturated after gas migration and the distribution of water content immediately after gas migration to study gas migration pathways. The gas migrated through the entire cross-section of the specimen, and gas breakthrough occurred in the equilibrium swelling pressure range approximately. Subsequently, the gas flow rate reached a sufficient large value when the gas pressure was approximately twice the equilibrium axial pressure (the sum of swelling and confining pressures), which excluded the back pressure. Although the gas migration pathway was not visible when the specimen was observed immediately after gas migration, the water content distribution showed that several parts of the specimen with lower water content were connected in the direction of gas migration. After resaturation, the change in permeability was within a limited range—two to three times larger than that before gas migration for each type of bentonite in SW. This slight change suggests that gas migration creates a pore structure that cannot be sealed via crystalline swelling of montmorillonite in SW, even if highly compacted bentonite is used under a constant-volume condition. |
| first_indexed | 2024-04-10T22:20:40Z |
| format | Article |
| id | doaj.art-34da5af715b6450793b8d447fa5cff27 |
| institution | Directory Open Access Journal |
| issn | 1674-7755 |
| language | English |
| last_indexed | 2024-04-10T22:20:40Z |
| publishDate | 2023-01-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Journal of Rock Mechanics and Geotechnical Engineering |
| spelling | doaj.art-34da5af715b6450793b8d447fa5cff272023-01-18T04:30:15ZengElsevierJournal of Rock Mechanics and Geotechnical Engineering1674-77552023-01-01151216226Saturated hydraulic conductivity of compacted bentonite–sand mixtures before and after gas migration in artificial seawaterYasutaka Watanabe0Shingo Yokoyama1Misato Shimbashi2Yoichi Yamamoto3Takahiro Goto4Sustainable System Research Laboratory, Central Research Institute of Electric Power Industry, Chiba, Japan; Corresponding author.Sustainable System Research Laboratory, Central Research Institute of Electric Power Industry, Chiba, JapanSustainable System Research Laboratory, Central Research Institute of Electric Power Industry, Chiba, JapanScience and Technology Department, Nuclear Waste Management Organization of Japan, Tokyo, JapanScience and Technology Department, Nuclear Waste Management Organization of Japan, Tokyo, JapanTo understand the self-healing property of an engineered barrier for radioactive waste disposal, the hydraulic conductivity of compacted bentonite–sand mixtures saturated with artificial seawater (SW) before and after gas migration was examined. Na- and Ca-bentonites were mixed with fine sand at a ratio of 70% bentonite in dry weight. Two aspects were considered during the experiment: the hydraulic conductivity of the specimen that was resaturated after gas migration and the distribution of water content immediately after gas migration to study gas migration pathways. The gas migrated through the entire cross-section of the specimen, and gas breakthrough occurred in the equilibrium swelling pressure range approximately. Subsequently, the gas flow rate reached a sufficient large value when the gas pressure was approximately twice the equilibrium axial pressure (the sum of swelling and confining pressures), which excluded the back pressure. Although the gas migration pathway was not visible when the specimen was observed immediately after gas migration, the water content distribution showed that several parts of the specimen with lower water content were connected in the direction of gas migration. After resaturation, the change in permeability was within a limited range—two to three times larger than that before gas migration for each type of bentonite in SW. This slight change suggests that gas migration creates a pore structure that cannot be sealed via crystalline swelling of montmorillonite in SW, even if highly compacted bentonite is used under a constant-volume condition.http://www.sciencedirect.com/science/article/pii/S1674775522000701BentoniteGas migrationHydraulic conductivitySeawater (SW)Self-healing |
| spellingShingle | Yasutaka Watanabe Shingo Yokoyama Misato Shimbashi Yoichi Yamamoto Takahiro Goto Saturated hydraulic conductivity of compacted bentonite–sand mixtures before and after gas migration in artificial seawater Journal of Rock Mechanics and Geotechnical Engineering Bentonite Gas migration Hydraulic conductivity Seawater (SW) Self-healing |
| title | Saturated hydraulic conductivity of compacted bentonite–sand mixtures before and after gas migration in artificial seawater |
| title_full | Saturated hydraulic conductivity of compacted bentonite–sand mixtures before and after gas migration in artificial seawater |
| title_fullStr | Saturated hydraulic conductivity of compacted bentonite–sand mixtures before and after gas migration in artificial seawater |
| title_full_unstemmed | Saturated hydraulic conductivity of compacted bentonite–sand mixtures before and after gas migration in artificial seawater |
| title_short | Saturated hydraulic conductivity of compacted bentonite–sand mixtures before and after gas migration in artificial seawater |
| title_sort | saturated hydraulic conductivity of compacted bentonite sand mixtures before and after gas migration in artificial seawater |
| topic | Bentonite Gas migration Hydraulic conductivity Seawater (SW) Self-healing |
| url | http://www.sciencedirect.com/science/article/pii/S1674775522000701 |
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