2011 Fiscal Year Final Research Report
Simplified protective structure against debris flow for safe transportation in mountainous region
| Project/Area Number |
22656105
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| Research Category |
Grant-in-Aid for Challenging Exploratory Research
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| Allocation Type | Single-year Grants |
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| Research Field |
Geotechnical engineering
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| Research Institution | The University of Tokyo |
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Principal Investigator |
TOWHATA Ikuo 東京大学, 大学院・工学系研究科, 教授 (20155500)
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| Co-Investigator(Kenkyū-buntansha) |
UCHIMURA Taro 東京大学, 大学院・工学系研究科, 准教授 (60292885)
YAMADA Suguru 東京大学, 大学院・工学系研究科, 助教 (70451789)
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| Project Period (FY) |
2010 – 2011
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| Keywords | 斜面崩壊 / 土砂崩落 / ロックシェッド / 衝突圧 / 模型実験 / DEM数値解析 |
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| Research Abstract |
Damage investigations that were conducted after such significant earthquakes in mountainous regions as the Niigata-Chuetsu earthquake in 2004, the Kashmir earthquake in Pakistan, 2005, and the 2008 Wenchuan earthquake in China demonstrated that problems were caused not only by the strong shaking and related phenomenon but also the post-earthquake instability of mountain slopes that were affected by the shaking. The latter means that slope failures during the period of emergency rescue and re-construction, road transportation at the bottom of unstable slopes is vulnerable to slope failures and is often stopped in particular during rain falls. To protect such important emergency activities from the slope problems, some structural measure was considered necessary. It was thought important further that the planned structure does not have to be so safe as normal structures in sloping ground because the road transportation to be protected is not of the ordinary type but are the emergency veh
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icles whose safety demand is not very high under special situations. Hence, the present research intended to investigate a simple and portable tunnel structure that mitigates the effects of debris flow on road transportation. The central aim was the evaluation of the impact force between debris flow and a protective structure. Because a study on a real-scale structure undergoing debris flow is impossible, a small-scale model study was made. By changing the amount of debris, debris types, the length of a slope, its gradient, and friction of the slope surface, tests were repeated on the distribution of impact pressure, its time history, and bending moment in an affected structure. Accordingly, a regression analysis was made to obtain an empirical formula for those values. The concerned structures were a vertical retaining wall and a tunnel. In addition, an energy viewpoint was introduced to investigate in a more rational manner the mechanism of generation of significant impact force. Furthermore, a discrete element analysis was developed to numerically reproduce the impact phenomenon in a greater scale. These efforts were made to apply results from small-scale model tests to a greater proto type in the field. Less
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