邊坡破壞所引發的土石災害時常造成生命與財產的重大損失，為了更準確地預測邊坡因降雨發生的變位與破壞的發生，本研究採用Force-equilibrium-Based Finite Displacement Method (FFDM) 對兩個邊坡滑動案例進行驗證分析。FFDM分析法是以極限平衡之切片法為基礎，加入土壤之剪應力-剪動位移雙曲線構成式，擴充成能計算滑動變位的邊坡穩定分析法。對於兩個有具有長期監測變位紀錄的案例檢驗FFDM分析法之適用性，在有效的參數範圍內，計算結果符合現地的量測值，證明了此改良法在工程上應用的可行性。本研究提出新的邊坡長期變位預測方法即利用第一次邊坡滑動量來反算破壞變滑動變位之相關力學參數再根據後續經由降雨引發之地下水位變化來預測後續的邊坡滑動量。驗證結果顯示，本方法不但可將相當複雜之破壞面力學參數簡單化，預測邊坡變位亦接近量測值，為實用之法。本研究並對於不同密度之砂土進行實驗室之中型直剪試驗，並蒐集9個不同地區與土壤案例之大型直接剪力試驗資料，以回歸分析求其雙曲線之應力-變位模型之控制參數，建立非線性剪應力-變位模型資料庫，提供後續邊坡邊位分析研究之參考。

Slope failures are major causes of natural hazards which are often associated with with great losses of lives and properties. In order to predict the rainfall-induced slope displacements and failures accurately, a force-equilibrium-based finite displacement method (FFDM) is used to analyze two slopes subjected to periodic rainfall-induced movements. The method is based on a conventional limit equilibrium slice method, with additional nonlinear shear stress vs. shear displacement relationships and displacement compatibility requirements. Case studies on two well-monitored slopes were performed to validate the FFDM. Results of back-analysis and parametric studies show that within the range of hyperbolic model parameters, the computed slope displacements agree with those measured in the field, revealing the applicability of FFDM to the slope displacement problems. Furthermore, a new procedure on predicting periodic rainfall-induced slope displacements based on the model parameters back-calcualted from the first event of slope movement is proposed. Some laboratory medium-size direct shear tests on a silty sand with various densities are performed in conjunction with some large-scale direct shear test data collected from the literatures are analyzed to establish a preliminary database of hyperbolic shear stress-displacement models to facilitate slope displacement analyses in the future.

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