| Project/Area Number |
18K13831
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| Research Category |
Grant-in-Aid for Early-Career Scientists
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| Allocation Type | Multi-year Fund |
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| Review Section |
Basic Section 22030:Geotechnical engineering-related
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| Research Institution | National Institute of Maritime, Port and Aviation Technology |
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Principal Investigator |
Sugiyama YURI 国立研究開発法人海上・港湾・航空技術研究所, 港湾空港技術研究所, 主任研究官 (50803615)
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| Project Period (FY) |
2018-04-01 – 2024-03-31
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| Project Status |
Completed (Fiscal Year 2023)
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| Budget Amount *help |
¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2020: ¥390,000 (Direct Cost: ¥300,000、Indirect Cost: ¥90,000)
Fiscal Year 2019: ¥2,730,000 (Direct Cost: ¥2,100,000、Indirect Cost: ¥630,000)
Fiscal Year 2018: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
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| Keywords | 粘土鉱物 / 変質 / 数理モデル / デコルマ帯 / スロースリップ / 粘土鉱物の変質 / 層間水の脱水 / 一面せん断試験 / 力学性状変化 / 深海底地盤 / サンプリング乱れ / 数値解析 / 相変化 |
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| Outline of Final Research Achievements |
To investigate the relationships between clay alteration and large-scale seafloor crust movement in the plate subduction zone decollement, mathematical models were developed to represent smectite illitization. Two types of models were developed in this study: 1. Mechanical modeling considering changes in mechanical properties due to smectite illitization, such as changes in friction characteristics, volume compression, and dilatancy characteristics. 2. Mechanical modeling based on the dehydration of interlayer water in smectite. Using model 1, the increase in shear strength with alteration was successfully expressed, leading to the sticking of the crust. Using model 2, the slow-slip mechanism was successfully explained.
Additionally, the results of sampling simulations showed that the gasification of dissolved gas caused an overestimation of in-situ strength. Therefore, it is necessary to set the initial stress conditions considering the disturbance of the sampling specimen.
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| Academic Significance and Societal Importance of the Research Achievements |
本研究では，今まで理学分野で検討されてきたスロースリップに関する知見に力学的知見を付与し，既往の研究でも得られている粘土鉱物の変質により発生する水圧に加え，プレート沈み込みによるせん断変形を評価することでスロースリップを再現する結果を得た点において学術的意義が高いといえる．また，これまで陸上地盤や水深の浅い海底地盤からのサンプリングではサンプリング時の溶存ガスの状態変化による乱れは無視できるほど小さかったが，水深100mを超えるような大水深からのサンプリングではその影響が無視できないことを明らかにした．これは，洋上風力開発など近年急速に進む海洋空間開発において社会的意義が高いといえる．
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