切片法分析均質不飽和邊坡抗滑動安全係數之研究

Safety Factor of Homogeneous Unsaturated Slope by Slice Method

白軒豪(Hsuan-Hao Pai)

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(2014年)

https://doi.org/10.6342/NTU.2014.03024

摘要

台灣地區的地形以山地地形所占比例最多，但隨著人口數量的成長以及都市
開發，人們的生活圈逐漸延伸至山地地區，而且台灣在夏季時常發生豪雨、颱風，在山區造成嚴重的災情，因此山坡地安全的檢核分析變得越來越重要。
傳統的極限平衡法分析邊坡滑動的安全係數，是將邊坡分為飽和以及乾燥部
分做切片分析，如此雖然可以讓分析得到的安全係數趨於保守，但卻將低了工程
的經濟性，實際邊坡情況會有部分區域是呈現不飽和狀態的，這些區域由於土體
不飽和狀態產生的吸應力能使土體的有效應力上升，進而使邊坡分析出的安全係
數提升，不但有助於工程成本的降低，分析結果也較貼近真實情況。
本研究利用GEO-STUDIO 中的SEEP/W 先對邊坡進行滲流分析，得到整個邊
坡的含水量分布以及壓力水頭分布，以有限邊坡抗滑動安全係數分析方法中的
Ordinary Method of Slices、Bishop Simplified Method 為基礎，在孔隙水壓
力計算的部分考慮吸應力的影響，以MATLAB 程式語言計算出該邊坡在考慮吸應
力下的抗滑動安全係數。

關鍵字

極限平衡法 ； 吸應力 ； 不飽和邊坡 ； 土水特徵曲線

並列摘要

In Taiwan, more than two third of land is mountain. As the country
continues to develop, people’s living places gradually expand into mountain
area. Rainstorm and typhoon often occur in summer and cause severe
damage. Thus, safety analysis in mountains becomes more and more
important.
When analyzing the factor of safety (FS) of a slope by conventional limit
equilibrium method, the slope is divided into a dry part and a fully saturated
part. Although a conservative FS can be obtained, it costs more in construction.
On the other hand, soil does not suddenly become fully saturated from a dry
situation. Saturation always changes from 0% to 100% gradually. As a result,
there is an unsaturated part in the slope.
From the literature, a special stress exists in the unsaturated soil, which is
named “suction stress“. Suction stress helps increase the effective stress in
the soil. Once effective stress gets higher, the FS of slope will increase too. It
not only makes the analytical result suitable in the current situation, but also
reduces the budget in the construction procedure.
The research conducts seepage analyses within the slope by Seep/w to
get the volumetric water content distribution and pressure head distribution in
the domain. Suction stress is than calculated analytically. Finally, limit
equilibrium analyses, including Ordinary Method and Simplified Bishop Method,
are carried out. The results are compared with the published data in literature.

並列關鍵字

slices method ； suction stress ； unsaturated slope ； soil water characteristic curve

參考文獻

Bishop, A. W. (1954). The use of the slip circle in the stability analysis of slopes.

Geotechnique, 5(1), 7-17.

Lu, N. and Likos, W. J. (2006). Suction stress characteristic curve for

Bishop, A.W. and Morgenstern, N. R. (1960). Stability coefficients for earth

slopes. Geotechnique, 10(4), 129-150.