利用有限元素法與極限平衡法進行九份國小邊坡穩定分析

Slope Stability Analysis of Jiu-Fen Elementary School Using the Finite Element Method and the Limit Equilibrium Method

本研究採用有限元素法與極限平衡法兩種不同分析方法，模擬九份國小邊坡之穩定性。極限平衡法較常用於邊坡穩定性分析，因可快速得到一潛在滑動面及其安全係數，但其假設較簡單較不考慮土壤之實際行為；而有限元素法之優點可採用較合理之土壤行為模式及邊界條件。由極限平衡法之臨界滑動面與有限元素法之位移向量場、應力場及塑性區分別進行比對探討。再者，比對兩方法之安全係數有何差別並加以討論。本研究顯示，由極限平衡法所求得之安全係數較有限元素法為高，而有限元素法之位移分析較符合邊坡漸進式破壞之行為，可知若將有限元素法搭配極限平衡法並配合現場監測數據，更可清楚分析邊坡之穩定性。

This study simulates the slope stability at Jiu-Fen elementary school, using the limit equilibrium method and the finite element method. The limit equilibrium method is usually used in slope stability analysis. It can find potential sliding surfaces and safety factors rapidly. The advantage of the finite element method is that it utilizes more reasonable soil behavior and boundary conditions. A critical sliding surface obtained by the limit equilibrium method can be compared with the displacement vector, stress field and location of plastic zone obtained by the finite element method. Furthermore, we can compare the safety factors produced by the two methods. This study shows that the safety factor from the limit equilibrium method is higher than that from the finite element method. The displacement analysis by the finite element method agrees well with the progressive slope failure. So, if we combine the two methods using monitored data in the field, we can analyze slope stability clearly.