降雨引致之非飽和邊坡穩定性分析

Rainfall Induced Unsaturated Slope Stability Analysis

王竣民(Jun-Min Wang)

指導教授 ： 葛宇甯

國立臺灣大學/工學院/土木工程學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201903198

摘要

台灣是全世界數一數二多雨的國家，一年四季皆有豐沛的降雨量，降雨是造成山區坡地災害的主因之一，近年來在做邊坡穩定性分析時已經將非飽和土壤的行為納入降雨入滲分析中，非飽和土壤存在著基質吸力，基質吸力為邊坡提供抵抗降雨入滲後產生的下滑力，考慮基質吸力後，分析時邊坡的安全係數會比沒有考慮基質吸力的安全係數還高。
本研究使用有限元素分析軟體PLAXIS 2D進行降雨入滲分析，探討邊坡之坡度、vG模型的擬和參數、滲透係數和降雨事件對非飽和邊坡之影響，利用基質吸力、安全係數、破壞滑動面等之間的關係判斷不同土壤參數各個行為的差異。研究結果顯示，浸潤帶是邊坡穩定性分析重要的因素，浸潤帶的產生讓邊坡表層基質吸力迅速降低，土壤的抗剪強度降低，容易造成邊坡滑動。在降雨強度低又長期降雨時，若滲透係數較大，雨水滲入土層後會流往更深層土壤並使地下水位提高。

關鍵字

邊坡穩定性分析 ； 有限元素法 ； 非飽和土壤 ； PLAXIS 2D

並列摘要

Taiwan is a rainy country in the world. There is abundant rainfall all year. Rainfall is one of the main causes of mountain slope disasters. In recent years, the behavior of unsaturated soil has been incorporated into the slope stability analysis. The matric suction is present in the unsaturated soil, and it provides force to resist the sliding force. After consider matric suction, the factor of safety will be higher than that without considering the matric suction.
In this study, PLAXIS 2D was used for slope stability analysis to investigate the influence of slope, fitting parameters of vG model, permeability coefficient and rainfall events on unsaturated slopes. Using the relationship between of the matric suction, factor of safety and failure surface to judge the difference of each soil parameters. According to the results, the wetting band is an important factor, it makes the matric suction of surface soil decrease rapidly, and the shear strength of soil is also decreases, which easily causes the slope to failure. At the rainfall event 3, if the permeability coefficient is large, the rainwater will flow to deeper soil and raise the groundwater level, and the saturation of the wetting band will be low relatively.

並列關鍵字

slope stability analysis ； finite element method ； unsaturated soil ； PLAXIS 2D

參考文獻

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