本研究在考慮不同降雨、土壤及初始土壤飽和度條件下，模擬無限邊坡土層之崩塌及滑動行為。模式的建立以消散波方程式及牛頓第二運動定律為基礎，考慮降雨入滲強度隨時間變化與未飽和的土壤條件，引入時變性降雨邊界條件與未飽和土壤參數，利用數值方法求解邊坡土層在降雨入滲下之破壞行為極其破壞後之與運動特性。研究結果顯示，降雨入滲的強度會控制崩塌的發生時間，但發生崩塌與否卻和降雨總入滲量、土體本身參數有關。由於土體降雨入滲的總壓力有著最大上限值，因此11種模擬土體可以區分為穩定土體與崩塌土體兩類，穩定土體受土壤本身性質之影響，當土體含坋土(Silt)量大於30%以上，或含黏土(Clay)量大於70%以上時，不會產生崩塌現象；而崩塌土體之破壞模式中，砂土、壤質砂土與砂質黏壤土會從土層頂部開始產生破壞，並逐漸影響到下方土層，進而引發整層土層滑動，砂質黏土與壤土反之從土層底部開始破壞。接著在本研究中可以知曉邊坡滑動發生時間受到降雨鋒型位置不同所影響，快到慢依序為前峰型、中峰型、後峰型，而滑動最後速度由快到慢依序為後峰型、中峰型、前峰型，且速度皆由土層上至下遞減，其中後峰型降雨可視為臨前降雨加上短延時暴雨，因此在相同初始飽和度條件下，後峰型所產生的滑動速度為最快。此外當初始土體飽和度越高，破壞發生的時間會越早、滑動最後速度會越快；而初始土體飽和度接近乾土時，土體不易產生滑動行為。

Landslide is a general, natural geomorphic erosion process on hillsides and can be threaten to people’s life and properties. In this study, landsliding along an infinite slope for diverse soil materials were analyzed under different rain infiltration, and initial saturation conditions. We developed a model that describes landsliding (i.e., triggering and movement) based on the factor of safety and the Newton's second law. Evolution of capillary pressure within a soil layer obeys a dissipative wave equation and the Fourier’s series is employed into boundary conditions to describe time-varying, unsaturated rain infiltration. Factor of safety is used to determine the depth and timing of landslide triggering and the Newton's second law is solved by the classical Simpson’s rule. Results show that the intensity of rain infiltration controls the timing of the landslide occurrence, but landslide triggering is mainly influenced by accumulated rainfall infiltration and soil properties. Here we categorize 11 soil properties used in this study into stable and unstable hillslopes. Numerical results for the stable hillslope indicate that landslide could not be triggered when its corresponding soil materials containing silt more than 30% and clay more than 70%. For unstable hillslopes, failures in sand, loamy sand, and sandy loam can be from the top, gradually propagating to soil-bedrock boundary; however, that in sandy clay and loam is occurred at soil-bedrock boundary directly. Hyetographs of rain infiltration can play an important role in landslide triggering, showing that advanced peak and delayed peak can lead to early landslide occurrence and the significant terminal velocity of landslide movement, respectively. In addition, the timing of landslide occurrence and the terminal velocity of its movement are also governed by initial soil saturation, indicating that the higher the saturation, the earlier the timing of landslide triggering and the faster the terminal velocity of landslide movement.

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