| Project/Area Number |
17K06534
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Research Field |
Structural engineering/Earthquake engineering/Maintenance management engineering
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| Research Institution | Okayama University |
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Principal Investigator |
Kimoto Kazushi 岡山大学, 環境生命科学研究科, 准教授 (30323827)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥4,680,000 (Direct Cost: ¥3,600,000、Indirect Cost: ¥1,080,000)
Fiscal Year 2019: ¥780,000 (Direct Cost: ¥600,000、Indirect Cost: ¥180,000)
Fiscal Year 2018: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2017: ¥2,470,000 (Direct Cost: ¥1,900,000、Indirect Cost: ¥570,000)
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| Keywords | ベントナイト / 粘土 / 水分 / 密度 / 超音波 / 不飽和 / 弾性波 / 水分量 / 群速度 / トモグラフィー |
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| Outline of Final Research Achievements |
This study is concerned with the ultrasonic method for the evaluation of water content and bulk density of unsaturated clay. Since acoustic properties of unsaturated clay has not been investigated systematically, we performed ultrasonic transmission test on compacted bentonite clay of various water content and bulk density. As the result, it was found that the ultrasonic wave velocity is correlated highly with the dry density, while the ratio of P- to S-wave velocity increases with the degree of water saturation. The set of ultrasonic velocity data obtained thus can be used to invert ultrasonic data to the water saturation and the dry density. To investigate the feasibility of ultrasonic spectroscopy further, surface waves in heterogeneous clay samples are visualized by a scanning laser ultrasonic detector. The result is encouraging in the sense that the heterogeneity of the sample appears in the measured ultrasonic wave field as the variation in the wave speed.
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| Academic Significance and Societal Importance of the Research Achievements |
高レベル放射性廃棄物の地層処分に用いられるベントナイト緩衝材の長期挙動を評価するにあたり、粘土中の水分や膨潤状態を知ることは重要である。そのためには、粘土の水分や密度の非破壊的に測定する技術が必要となるが、水分と密度の両方を計測可能な手法は今のところ存在しない。一方、本研究で対象とした超音波計測では、弾性波速度が媒体の水分と密度の影響を受けて変化するため、これら諸量間の関係を定量的に調べておけば、超音波計測結果から水分と密度の両方を推定することが可能となる。本研究はこのような原理による新たな超音波スペクトロスコピーが可能であることを初めて示し、その実現に必要な基礎データを整備したものである。
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