Changes in Slope Stability over the Growth and Decay of Japanese Cedar Tree Roots
Changes in Slope Stability over the Growth and Decay of Japanese Cedar Tree Roots
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DOI：
10.3390/f14020256
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发表时间：
2023-01
期刊：
影响因子：
2.9
通讯作者：
Y. Okada;F. Cai;U. Kurokawa
中科院分区：
文献类型：
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作者：
Y. Okada;F. Cai;U. Kurokawa
在日本，反复发生的浮木滑坡灾害已成为一个重大问题；因此，需要进行研究，以便更好地了解森林的功能，以实施适当的森林管理和预防此类灾害。研究了杉木树根对浅层滑坡起滑的影响。为了考虑滑坡体两侧根的影响，提出了一种新的滑坡体稳定性分析方法，将滑坡体简化为三棱柱模型。根系加固近似为单位面积上根系拔拔力的总和，考虑了树木种植后根系强度随树木生长和砍伐后树桩腐烂的变化。断根后的增强根强度随时间线性下降，到9年时已无强度保留。与此相反，新植株的增强根强度随时间呈logistic曲线增长；因此，种植后9年，根系强度仅略有增加，此时观察到最小的总增强根系强度。在1米分辨率的数字高程模型上，采用三棱柱法计算了茨城县森林盆地斜坡的安全系数，每隔5年计算一次。不稳定栅格数在10年时达到峰值，5-15年时边坡失稳风险较高。因此，在这一时期实施降低边坡失稳的森林作业对预防滑坡灾害具有重要意义。
In Japan, repeated driftwood landslide disasters have become a major issue; thus, studies are required to better understand forest function to implement appropriate forest management and prevent such disasters. We investigated the effect of Japanese cedar tree roots on shallow landslide initiation. To incorporate the effect of roots on the two side-flanks of the shallow landslide, we propose a new slope-stability analysis method in which the sliding block is simplified as a three-prism model. The root reinforcement was approximated by the sum of the root pullout forces over a unit area, incorporating changes in the root strength with the growth of the trees after planting and the decay of the stumps after cutting. The reinforced root strength after the stump-cutting decreased linearly with time, with no strength remaining at 9 years. In contrast, the reinforced root strength of the new plants increased according to a logistic curve with time; thus, the root strength increased only slightly up to 9 years after planting, and the minimum total reinforced root strength was observed at this time. The safety factor of the slopes in a forest basin in Ibaraki Prefecture was calculated using the proposed three-prism method at intervals of 5 years on a 1-metre-resolution digital elevation model. The number of unstable grids peaked at 10 years, and a higher risk of slope instability was observed at 5–15 years. Therefore, implementing forest operations for lowering slope instability during this period should be important to prevent landslide disasters.