2001 Fiscal Year Final Research Report Summary
STUDIES ON GEOMORPHIC POSITION AND TIMING OF REGOLITH SLIDE OCCURRENCE
| Project/Area Number |
11480098
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Natural disaster science
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| Research Institution | Tohoku University |
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Principal Investigator |
TAMURA Toshikazu Tohoku University, Graduate School of Science, Professor, 大学院・理学研究科, 教授 (00087149)
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| Co-Investigator(Kenkyū-buntansha) |
OTSUKI Yoshinori Tohoku University, Graduate School of Science, Assistant Lecturer, 大学院・理学研究科, 助手 (00272013)
HIRANO Shin'ichi Tohoku University, Graduate School of Science, Associate Professor, 大学院・理学研究科, 助教授 (10228801)
MATSUMOTO Hideaki Tohoku University, Graduate School of Science, Associate Professor, 大学院・理学研究科, 助教授 (30173909)
CHIBA Noriyuki Tohoku Institute of Technology, Faculty of Engineering, Associate Professor, 工学部, 助教授 (00104133)
MIYAGI Toyohiko Tohoku Gakuin University, Faculty of Letters, Professor, 文学部, 教授 (00137580)
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| Project Period (FY) |
1999 – 2001
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| Keywords | REGOLITH SLIDE / SLOPE FORM / REMOVABLE MATERIAL / CONVEX BREAK OF SLOPE / SOIL CREEP / SOIL STRATIGRAPHY / SOIL WATER / COLLUVIAL DEPOSITS |
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| Research Abstract |
Hydrogeomorphological and pedogeomorphological observations were carried out both in the fields and In the laboratory in order to obtain the knowledge on geomorphic position and timing of the occurrence of rain-induced regolith slides. The major results are as follows:
1) Soil creep is the major process of regolith movement on the upper slope segments in the hills around Sendai, northeastern Japan. Its rate ranges from 0 to several centimeters per year. Relatively great rate is recorded at the soil horizons/layers which fill bedrock hollows in rainy season every year and snow-melt periods in the case of extraordinary snow accumulation. B or BC horizon shows block type movement while flow type movement prevails in A horizon. Minor slide of B or BC horizon on sloping bedrock surface seems to induce flow of soil particles in overlying A horizon.
2) On the lower slope segments, the regolith, which is usually less than 1m thick and provided from the upper slope segments by the process as abov
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e, rapidly slides down with the volume of less than 1,000m^3 at a site in most case and the frequency of several hundred years. Rain which can induce regolith slides in the hills around Sendai is more than hundred and several tens of millimeters in total and about 35 mm/h in intensity, which leads to rapid increase of pipe flow st several soil horizons/layers
3) Most active pipe flow occurs at B or BC horizon. Pipe flow discharge at respective soil horizons/layers and its share changes in response to intensity and duration of rainfall. The changing response of pipe flow at several horizons/layers depends on high percolation rate at O and A horizon and large storage capacity at B or BC horizon.
4) More intense rainfall can induce regolith slides on the upper slope segments, mostly the headmost walls, also, particularly in the hills with thick saprolite and high relief. It seems to be due to concentration of percolated water to the pipes which have their outlets on the upper part and are inactive in the case of weak rain. Less
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[Publications] Tamura, T., Kato, H, Furuta, T., Matsubayashi, T., Chattarjee, D. and Li, Y.: "Occurrence of rain-induced regolith slides on segmented hillslopes"Transaction, Japanese Geomorphological Union. Vol. 22 (Spec.). C-237 (2001)
Description
「研究成果報告書概要(欧文)」より
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