| 研究課題/領域番号 |
16F16378
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| 研究機関 | 京都大学 |
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研究代表者 |
中北 英一 京都大学, 防災研究所, 教授 (70183506)
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| 研究分担者 |
WU YING-HSIN 京都大学, 防災研究所, 外国人特別研究員
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| 研究期間 (年度) |
2016-11-07 – 2019-03-31
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| キーワード | vegetation / groundwater / Poroelasticity / Mohr-Coulomb theory / Finite element analysis / hillslope stability / climate change |
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| 研究実績の概要 |
It is universally accepted that the extreme climate becomes more frequent. Our environment becomes warmer, and rainstorms tend to be intense. Global warming directly or indirectly influences hillslope vegetation, landform and stability, which are the dominant factors for slopeland hazard occurrence. As being the origin of slopeland hazards, landslide is our analysis target. We aim to propose a new model to couple among landform evolution, hillslope vegetation, and hillslope stability for assessing landslide susceptibility trend under climate change influence. In FY2016, our main objectives are successfully finished as planned. The landslide model is to identify unstable zones prone to landslide on steep and vegetated hillslopes. With mechanical approaches, we have developed a landslide model considering transient vegetation surcharge and root-reinforcement and groundwater motion. Tree-growth allometric equations are used for quantitative modelling of transient tree surcharge and root-reinforcement. Poroelasticity is used for evaluating stress equilibrium in hillslope under given groundwater flow and vegetation forcing. Then, Mohr-Coulomb failure theory is applied to find the unstable zones. The three parts above are numerically calculated by using the finite element method. We have performed case study of saturated hillslopes in different two-dimensional shapes. The result has been presented in the conference.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
In FY2016, we have developed a landslide model, and performed the analyses of two-dimensional problems. Now we are extending our landslide model for three-dimensional problems. As the finite element method is used in our landslide model, it requires a mesh tool for processing three-dimensional topography and soil layer. However, there are no convenient tools or programs available for our usage. Thus we are now developing our own tool for it.
Besides, to consider the groundwater motion in unsaturated hillslopes, we are also modifying the model of groundwater flow, which is the key component in our methodology. Because in vegetated and steep hillslopes, rainfall reaching on slope surface usually infiltrates to the bedrock interface in a short time, thus groundwater table almost responds to rise immediately in the bottom of a thin soil layer. Also, due to slope steepness, the variation of groundwater table normal to the slope surface can be reasonably ignored. Based on the two reasons above, we are modifying the groundwater model by using the Dupuit theory with a given precipitation input to approximately calculate groundwater distribution and surface runoff volume, which are main components for our following analysis.
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| 今後の研究の推進方策 |
This research has three phases, including development of models of landslide and landscape evolution, and analyses using different climate simulation datasets. In FY2017, we would like to finish model development, and to start performing some preliminary case analyses. The plan is briefly mentioned in the following.
As being progressing currently as planned, the modification of groundwater model and the extension of our model to three-dimensional problems are expected to be finished in half a year. Next, we will begin to develop the landscape model by using the output of groundwater flow from our landslide model for simulation of the evolution process of topography caused by runoff-induced surface erosion. This part is expected to be finished in four months. After development, we shall integrate all parts with each other, and preform model verification. Finally, we will use our developed model to conduct preliminary case studies, and start to analyze the tendency of hillslope safety responding to the precipitation under climate change influence.
To sum up, we expect to finish all model development, and to begin utilizing our new model for the analysis of climate change impact on slopeland in FY2017.
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