本文以蘇花公路115.9k邊坡崩塌區為主要研究對象，利用不同時期數值高程模型、地形圖與遙測影像等加值資訊，搭配現場地質調查與地形分析結果，初步評估研究範圍之歷史地形變化特性與山崩機制。另經由現地調查與力學實驗成果，建構三維有限元素穩定分析模型，並搭配分離元素法進行坡體穩定分析與災中山崩運移過程模擬。研究成果顯示，位於115.9k上游變質岩邊坡具有岩體變形之特徵，其中上游侵蝕溝周緣邊坡均具坡趾見光與崖頂張裂縫發展之跡象，且仍有部分不穩定塊體停滯於上游；當高強度降雨發生時，其源頭區岩屑/岩體即可能發生滑動，其運動速度約在5~20 m/sec之間，接著高陡變之地形將使岩屑/岩體滑動轉為高速(>30 m/sec)之岩屑崩滑，並以極快之運動速度運移至下游，順勢摧毀蘇花公路115.9k，並於下游出海口形成沖積扇。

This study focused on the landslide case at Su-Hua Highway 115.9k, Taiwan. A preliminary investigation was conducted on geomorphologic features change and landslide mechanisms using digital elevation models, geographical maps, and remote sensing images at different times in conjunction with geological surveys and analysis results. Using the results of geological surveys and physical model experiments, we constructed a discrete element method to simulate the process of landslide movement.
The results revealed deformation in the metamorphic rock slopes upstream of 115.9k. The slopes around the erosion gully upstream presented visible slope toes cutting and tension cracks at the crest as well as unstable rock masses. According to the results of numerical simulation for typhoon Megi event, intense rains could induce slippage in the rock debris/masses in the source area, initially at a speed of 5-20 m/sec.
Subsequently, steeper terrain could cause the rock debris/masses to accelerate to form a high-speed (>30 m/sec) debris slide quickly moving downstream to form an alluvial fan downstream by the sea.