2020 Fiscal Year Final Research Report
Elucidation of formation conditions and morphological and dynamic characteristics of meg-ripples by field measurements and wind tunnel experiments
| Project/Area Number |
16K01219
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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 |
Geography
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| Research Institution | Tottori University |
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Principal Investigator |
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| Project Period (FY) |
2016-04-01 – 2021-03-31
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| Keywords | メガリップル / 粗粒粒子 / Great Sand Dunes / 鳥取砂丘 / 風洞実験 / 凹面状断面形態 / 砂面低下 / ポリプロピレン粒子 |
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| Outline of Final Research Achievements |
In the Tottori Sand Dunes, mega-ripples with a wavelength of more than 1 m appeared on the edge of the exposed volcanic ash layer for three years from 2013 to 2015. Taking this as a hint, a wind tunnel experiment was conducted, and it was clarified that the amount of polypropylene coarse-grained particles that simulated the aggregated particles of volcanic ash sprayed on the sand surface was one of the critical conditions for forming mega-ripples. In addition, it was confirmed by wind tunnel experiments that mega-ripples are likely to appear only in the area where the sand surface is lowered. This could be confirmed by the morphological characteristics of mega-ripples found in the Great Sand Dunes of the United States.
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| Free Research Field |
地形学
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| Academic Significance and Societal Importance of the Research Achievements |
メガリップルを実験で形成模擬できた初めての研究となった。粗い粒子の共存がメガリップルの必要条件であることは，従来知られていたが，その量比の重要性は認識されていなかった。またメガリップルは砂面の低下傾向で出現しやすい砂床形であることが，実験で確認されたことより，現地でメガリップルが限られた区間にしか観察されない理由が解明された。つまり砂面が低下すると，必ず飛砂が発生し，その下流側では砂面が低下しにくくなるためである。公園や寺院の境内など多くの人が行き交う場所には，しばしばメガリップル類似地形が観察される。形成メガニズムの類似性を探る必要がある。
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