1999 Fiscal Year Final Research Report Summary
Study on General Hazard Evaluation of Volcanic Disaster Affecting Agriculture and Foestry in Southern Kyushu
| Project/Area Number |
09660167
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
林学
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| Research Institution | Miyazaki University |
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Principal Investigator |
TANIGUCHI Yoshinobu Miyazaki University, Department of Agriculture, Professor, 農学部, 教授 (70041051)
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| Project Period (FY) |
1997 – 1999
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| Keywords | pyroclastic flow / pyroclastic serge / distributuion of temperature / mud-debris flow / age determination / pyroclastic carbonized wood / old volcano / slope failure |
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| Research Abstract |
The experimental results of pyroclastic flow found that the pyroclastic flow would cause a great damage by its serge and big stones in it would reach as far as lower steam. The surveying result of the distribution of temperature on the earth surface of Mt. Kirishima showed that high temperature zone in the cone of Mt.Shinmoe has been moving west. The scale of one pyroclastic flow of Mt.Kirishima was estimated in 10ィイD16ィエD1〜10ィイD17ィエD1 mィイD13ィエD1. Melting test of the pyroclastic pieces found that its temperature might be 700℃〜1000℃. The volcanic activity of Mt.Shinmoe has kept to repeat every 200〜300 years from the age determination of pyroclastic carbonized wood. The geomorphological and geological investigation about the mud-debris flow which took place in Masaki of Ebino City in 1972 was carried out. It is a type of mud-debris flow occurred on the slope of old volcanoes. These mountain slopes are always subject to work of volcanic acid gas and the soil mechanical strength has much d
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eteriorated. It means that large scale of slope failure may occur on the slope of Mt. Kirishima. The result of hydrological surveying in the torrents of Masaki found that there were two types of underground water; shallow type and deep type. Velocity of the debris flow which took place in Harihara River of Izumi City, Kagoshima Prefecture, in 1997 was estimated in 3.5m/sec(14〜23m/sec in fact) from the rheological experimental result. The occurrence of this mud-debris flow was due to mechanical deterioration of the mountain composed of the old volcano "Mt.Yahazu". It means that the houses in the Harihara district were hit by flood first and the main debiris flow followed after it. It was proved by the way of experimental simulation that the cross section of Harihara sabo dam was unsufficient for its mechanical stability and the residents had only 51 seconds to evacuate after the debris flow had passed over that dam. It means that there is serious problem for prevention disaster on the top of fluvial fan and it is very difficult to estimate design stress of a sabo dam. Less
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