| Project/Area Number |
04452289
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
林学
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| Research Institution | Saga University, Department of Civil Engineering. |
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Principal Investigator |
KISHIHARA Nobuyoshi Saga Univ. Dep. Civil Eng.Prof., 理工学部, 教授 (40003769)
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| Co-Investigator(Kenkyū-buntansha) |
IWAO Yuushiro Saga Univ. Dep. Civil Eng. Prof., 理工学部, 教授 (80039289)
ONIZUKA Katsutada Saga Univ. Dep. Civil Emg. Prof., 理工学部, 教授 (20037948)
YAMAGUCHI Isao Tokyo Univ. Dep. Agriculture. Prof., 農学部, 名誉教授 (30011836)
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| Project Period (FY) |
1992 – 1993
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| Project Status |
Completed (Fiscal Year 1993)
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| Budget Amount *help |
¥6,000,000 (Direct Cost: ¥6,000,000)
Fiscal Year 1993: ¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1992: ¥4,200,000 (Direct Cost: ¥4,200,000)
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| Keywords | Large-scale collapse / Debris flow / Sedimentation / Groundwater level / Pore water pressure / Water temperature / Effective rainfall / Desolative stream / 間隙水圧 / 斜面崩落 / 斜面の安定 / 地温 |
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| Research Abstract |
The purpose of this study was to ascertain predictive factors in the large scale collapse of Mt.Mayumama, located in sediment yield from the large collapsed site formed in 1792 after the eruption of Mt.Unzen. The amount of collapsed soil at that time wasthe second highest and the 15,000 deaths the highest in Japanese sediment disaster history. The cause of this large collapse is assumed to be the combined action of extreme ground water rise due to volcanic activity and the large epicentral earthquake. The volcanic activities of Mt.Unzen from 1991 to present may possibly cause another large collapse at Mt.Mayuyama. Therefore, ground water change at various locations in Shimabara city has been monitored in order to identify predictive indications of collapse. The results, of ground water monitoring were :
1)An unusualrise in ground water level and high water temperature were observed in 1992 in southern part of the city. 2)After analysis, ground water in a well at a depth of 10m had the same composition as at 300m, the later beind hot spring water.
3)The same chemical composition with hot spring was detected in a spring on Mt.Mayuyama.
Results concerning sediment yield were as follows : 1)Through analysis of 12 aerial photograhs taken over the last 45 years, mud flows, a dominant cause of sediment yield, occurred after daily rainfall of more than 300m of earthquakes registering higher than 4 on Japanese scale on the slope of the collapsesite.
2)From several topographical surveys in 1992-1993, it was evident that mud flows occur after a daily rainfall of less thanl year of the return period. This indicate that the slope layr has been weakened by the recent volcanic activity of Mt.Unzen.
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