平面邊坡已在大地工程中被廣泛研究與使用，然而在自然界中可以觀察到一些具有凹形輪廓的邊坡，此證據表明凹形邊坡可能是更穩定的結構，近幾年的研究也透過數值模擬與物理模型實驗支持此論點。為了進一步探討凹形邊坡之穩定性，本研究使用中央大學地工離心機進行離心模型試驗，在靜態與動態試驗中觀察凹形邊坡與平面邊坡之破壞行為並分析。試驗之邊坡皆由70% 石英矽砂混合30% 高嶺土於最佳含水量下夯實而成，坡角為70o，凹形邊坡之坡面幾何條件由圓弧定義。靜態試驗中，利用人造重力場逐漸增加試體內部之重力，直至邊坡達到臨界坡高而誘發破壞；動態試驗中，在40 g穩定重力場下輸入數個振動事件直至邊坡達到破壞，觀察滑動塊體位移量與破壞行為。 由試驗結果得知：(1) 靜態試驗中，平面邊坡於45 g產生張力裂縫，凹形邊坡則於50 g產生裂縫。平面邊坡能達到臨界坡高約為12.10 m；凹形邊坡之臨界坡高約為13.86 m。試驗結果顯示坡面幾何條件在靜態下會影響邊坡之穩定性，其中凹形較為穩定。(2) 動態試驗中，透過位移量-振動事件歷時與影像進行分析，凹形邊坡能承受之振動事件較多，且極限位移量為為平面邊坡之1.35倍。由此判斷地震狀態下，凹形邊坡仍是較穩定之配置。 ;Planar slopes are widely studied in geotechnical engineering. However, some slopes with concave profiles were observed in the field. The phenomenon implies that concave slopes might be a more stable configuration in nature, and recent studies have supported this theory through numerical simulations and physical models. In order to further discuss the stability of concave slopes, several centrifuge modeling tests were conducted in this study by geotechnical centrifuge of NCU, and the failure behaviors in static and dynamic tests can be observed. The results show that: (1) In the static test, the tension crack appeared earlier on the top of planar slope. The critical height of the planar slope can reach to 12.10 m, and the concave one is about 13.86 m. The result shows that the geometric condition would affect the stability of the slope under static conditions, and the concave shape is more stable than planar one. (2) In the dynamic test, the concave slope can bear more shaking events, and the allowable displacement is 1.35 times as much as planar one. Therefore, as other studies, this research also shows that the concave slope is a more stable configuration than planar slope under the seismic or static condition.
