本研究為期三年，將以力學觀點分別探討降雨對引致邊坡淺層崩塌及土石流之機制。計畫內容擬以現場調查、理論及實驗方式三方面來進行淺層邊坡破壞與崩塌轉化成土石流之研究。邊坡破壞主要與(1)土壤摩擦角、(2)孔隙水壓力、(3)土壤凝聚力及 (4)土體裂縫條件等四個參數有密切的關係。邊坡破壞後產生崩塌，而崩塌過程之滑動面流體化層顆粒溫度逐漸升高、顆粒碰撞激發超額孔隙水壓提高液化的潛能，而逐漸發展為土石流。逐年課題分述如下： (1) 第一年 降雨入滲及逕流對飽和及非飽和邊坡淺層崩塌發生機制之影響：淺層破壞發生之條件，主要與環境之地形條件，雨量分佈，土壤條件，以及土壤初始水分含量息息相關。本研究擬根據G-A 入滲公式，結合無限邊坡理論，計算出非飽和邊坡於降雨過程中隨時間及土層深度變化之穩定性，並由現場地文及水文基本資料配合降雨強度，可求得不同降雨強度及不同破壞時間之關係，並且以室內水槽實驗驗證本模式之正確性。 (2) 第二年 邊坡淺層崩塌轉化為土石流之條件 : 崩塌轉化成土石流必須經過土體液化過程，液化常發生在接近滑動面的地方，滑動土體將持續運動且在滑動土體與地表間的邊界上持續液化。本研究擬以理論及數值來分析滑動土體之液化過程，並探討液化過程與土體強度、含水量、孔隙率、與內摩擦係數等參數之關係函數。本研究並擬以輸送帶實驗來分析崩塌液化土體之速度剖面。 (3) 第三年 裂縫對飽和及非飽和邊坡淺層崩塌發生機制之影響:降雨時坡面逕流更會順著裂縫下滲土體，造成坡面的不穩定度提高。本研究擬以理論及實驗探討裂縫對崩塌型土石流發生條件之影響，並求得斜坡裂縫特性(裂縫寬度、裂縫深度、裂縫間距等)對土體滲漏破壞之臨界降 。The mechanisms of debris flows triggered by shallow landslides will be explored in this proposed study , in a three-year period , by employing field study , theoretical analysis , and by experimental work. The key items related to the shallow slope failure are (1) the angle of internal friction of the soil , (2)pore-water pressure , (3) the cohesional component of the soil strength (4) crack conditions. During the process of landslide, the landslide may be gradually transformed into the debris flow due to increasing granular temperature in fluidized layer and the collision among grains. In the first year (93/8~94/7): Influence of unsaturated and saturated slope shallow landslides triggered by interaction between infiltration and runoff: This study takes account of negative pore water pressure and analyzes how pore water pressure of the wetting front affects the stability of strata. The failure in strata will be distinguished into two types: one is above the wetting front, and the other is below the wetting front, so as to understand the effect of infiltration on strata stability, and correspondingly to understand the effect on the initiation of potential debris flow events. In the second year (94/8~95/7): The threshold condition of shallow landslides induced debris flow: The parameters of landslide transferring to the debris flow will be specified by experimental work and theoretical analysis . The parameters include the coefficient of friction , granular temperature and excess pore-water pressure . Coefficient of friction being function of fluidized thickness , relation between granular temperature and coefficient of friction and relation between the velocity of mass and granular temperature . In the third year (95/8~96/7): The threshold conditions of rainfall-induced shallow landslides with cracks : A conceptual model, as well as experimental verification, will be proposed in this study to describe the threshold conditions of rainfall-induced shallow landslides with cracks. The required total rainfall triggering the landslide decreases with the increasing rainfall intensity for given crack conditions . This model can evaluate the effects of cracks on the threshold conditions, and it can be used to predict the occurrence of landslides under different scenarios. 研究期間：9308 ~ 9407
