2021 Fiscal Year Final Research Report
Prediction methods of sediment discharge areas due to slope failures caused by earthquake in volcanic ash deposited areas
| Project/Area Number |
19H02393
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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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| Review Section |
Basic Section 25030:Disaster prevention engineering-related
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| Research Institution | Hokkaido University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
桂 真也 北海道大学, 農学研究院, 助教 (40504220)
笠井 美青 北海道大学, 農学研究院, 准教授 (80294966)
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| Project Period (FY) |
2019-04-01 – 2022-03-31
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| Keywords | 胆振東部地震 / 斜面崩壊と崩土 / 亀裂 / 機械学習による斜面危険度評価 / 浸透量解析 / 斜面内部の水分状態 / 剛体滑動モデル / 滑動型表層崩壊氾濫・堆積区域設定手法 |
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| Outline of Final Research Achievements |
Machine learning was conducted on the slope failures that occurred in Atsuma due to the 2018 Hokkaido Iburi East Earthquake, using pre- and post-earthquake LP data, which revealed that slopes with cracks appearing on the ground in advance were vulnerable and at high risk of slope failure. In addition, groundwater analysis was conducted to reproduce the moisture condition inside the slope at the time of the earthquake. The results suggest that the water retention property of the slip surface and the permeability of the layer below the slip surface are the key points to focus on when identifying slopes in danger of failure. Furthermore, we developed a method to establish a two-dimensional spreading and deposition area for a block sliding surface failure by calculating the reach of the collapsed soil using a rigid body sliding model (the dynamic friction coefficient was measured using field sediment samples) and giving the average value of the collapse width in the transverse direction.
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| Free Research Field |
砂防工学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究により、地震前、地震後の斜面の微地形(亀裂)に着目した機械学習による崩壊危険度評価手法、火山灰の堆積構造を踏まえた浸透流解析による斜面崩壊の箇所の抽出方法、火山灰が堆積した緩勾配斜面での斜面崩壊のメカニズム(地震動による間隙水圧の急上昇とすべり面境界付近の火山灰層の泥濘・強度低下、斜面安全率の低下)、滑動型表層崩壊による崩土の氾濫・堆積範囲の再現・予測手法を提案できた。これらの成果は、全国や海外においても火山灰が堆積した山腹斜面が地震によって崩壊した場合の土砂災害危険区域の設定(ハザ－ドマップの作成)や対策工法の開発に大きく貢献できる。
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