本研究在中央大學土木系大型力學實驗館離心模型實驗室進行物理模型試驗，探討在重力、降雨和地震等不同自然營力作用下的邊坡破壞行為，試驗使用80 %石英砂混和20 %高嶺土的混和土壤，並於最佳含水量條件下夯實製作模型邊坡。第一個系列試驗主要改變邊坡內部薄礫石層的傾向，並逐漸增加試體所受到的重力場，直至邊坡發生破壞，用以瞭解邊坡內部若含一透水之薄礫石層對邊坡穩定性的影響；此外，亦規劃三組試驗探討降雨及地震條件下邊坡的破壞行為。離心模型模擬過程中皆透過不同角度的相機記錄破壞過程，從照片中可以追蹤破壞面的發展與位置，試驗前後邊坡的崩塌與堆積行為則以雷射位移計掃描獲取高程與位移數據。 離心模型試驗結果顯示（1）薄礫石層的傾斜方向會影響邊坡的穩定性，當薄礫石層的傾向與坡面傾向相同時，邊坡的安全係數最小；但是在邊坡幾何條件、土壤材料和夯實度相同情況下，邊坡破壞面位置則不因薄礫石層的傾角而改變。（2）降雨強度會影響土壤的入滲範圍，而水在土壤的滲透能力會影響地表逕流情況；在總降雨量相同時，降雨及地表逕流引致的坡面侵蝕與坡趾的堆積範圍幾乎一致。（3）地震對邊坡穩定性的影響明顯大於重力和降雨條件，從張力裂縫分布的位置來看，影響區域為坡頂至0.8倍邊坡高度的範圍。;This study focused the failure behaviours of slope stability under gravitational, rainfall and earthquake condition. A series of centrifuge model tests were conducted to study the slope stability at the Experimental Center of Civil Engineering, National Central University. Plane – strain slope models were prepared from sand which is mixed with fine content of 20% (kaolinite) and compacted at optimum water content. Under gravitational condition, three models were carried out different directions of a gravel layer placed inside a slope. During test, the acceleration was gradually increased until the slope failure occurred; the model failing at the lowest acceleration would be chosen to observe the behaviours of slope under rainfall and earthquake condition. The process of failure was recorded through cameras during centrifuge spinning. Additionally, the failure surface was traced from the photos; the elevation and displacement were obtained from scanned data before and after the tests. The results indicated the effects of the direction of the gravel layer on slope stability, that the slope with a normal inclination of the gravel layer was the most unstable in three directions (normal, reverse, horizontal). Moreover, the failure surface of the models was almost the same under the same slope geometrical conditions, soil materials and compaction degree. An observation showed that the behaviours of erosion induced on slopes by rainfall were almost similar with a constant of cumulative rainfall. The effect of intensity played an important role on the infiltration of water. Additionally, earthquake significantly impacted on slope stability more than gravity and rainfall condition, which had a maximum effective zone of 0.8 time of slope height.
