這幾年溫室效應與地球暖化影響，台灣沿海堤防的傷害屢屢更加嚴重。所以近年來利用地工合成物來使堤防結構達到加勁效果，但因海水之侵蝕，時常會出現基腳掏空的情形，故應重視基腳掏空對於加勁堤防穩定性之影響。本研究採用長150 mm，直徑1.96 mm鋼針模擬二向度 (Two-dimensional)均勻顆粒土壤，製作高433 mm之加勁堤防模型，利用加勁堤防模型來探討基腳掏空情形下之變化，並以10個可分離雙向荷重元量測牆面應力，採用熱融不織布黏貼應變片量測加勁材應力，並以變位計量測牆體位移以及背填土之沉陷量。
利用不同坡度與加勁材長度建構加勁堤防進行基腳掏空試驗，由試驗結果可知：一、加勁材長度的增長有助於承受加勁堤防基腳掏空的能力，也可以有效提升背填土抗沉陷的能力，但當長度增長到一個程度後加勁材長度的效益便會減少，使得承受基腳掏空的能力無法繼續提升，但背填土抗沉陷的能力依舊隨著加勁材長度增長而增加。二、坡度30°的加勁堤防，只要加入少許的加勁材，就可以使得加勁堤防基腳受到掏空的能力大大的增加，所以若現地允許，使用坡度30°的加勁堤防並配合少許的加勁材，便可以得到非常有效的抗基腳掏空效果，而且成本也將會比坡度60°加勁堤防來的經濟實惠。三、若背填土的位置已經離開加勁堤防的加勁區，當加勁堤防受到基腳開挖時，背填土並不會受基腳掏空的影響而產生沉陷，沉陷只會產生在背填土受加載的時候，所以基腳掏空並不會影響已經離開加勁區的背填土。

SUMMARY
The effect of toe scouring on the stability of geosynthetic-reinforced dykes was investigated using model dykes backfilled with an idealized 2-D backfill. In addition, the effect of reinforcement configuration was also investigated. The following conclusions were obtained:
1. The bearing capability against toe scouring and the resistance of backfill against can be significantly improved via the use of geosynthetic reinforcement. By increasing the length of reinforcement, especially for those near the base of the dyke, the above-mentioned effect can be further increased.
2. The bearing capability against toe scouring of the 30° slope reinforced dyke can be enhanced significantly by using a relatively small amount of the reinforcing material, comparing with that needed in the case of a steep-faced (60°) dyke, in order to achieve a similar degree of dyke stability.
3. The effect of soil reinforcement against toe scouring is also influenced by the extend (or size) of toe scouring. Test results show that the contribution of reinforcing materials is more significant in the case of small scale toe scouring than that in the case of large-scale toe scouring.

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