台灣位處環太平洋地震帶，頻繁的造山運動使得台灣地形山多平原少，大大小小的地震以及所處的緯度在夏秋之際常有颱風肆虐，造成邊坡不穩定，常因此發生邊坡破壞，對人身安全及建設造成威脅。 胡家豪(2019)以離心機試驗及PFC數值模擬探討高傾角逆向坡的破壞機制，以不同的岩層厚度及解壓長度作為變因討論，當岩層厚度越薄、解壓長度越長，逆向坡越容易發生撓曲傾覆破壞。鄭皓文(2019)於高傾角逆向坡加入第二節理，探討第二組節理對不同的岩層厚度及解壓長度造成的影響，研究結果顯示當岩柱的細長比大時，其破壞行為會以撓曲傾覆破壞為主，只有在適當的長寬比才會發生塊體傾覆破壞。 本研究延續胡家豪(2019)，於高傾角逆向坡加入降雨之因素，進行物理試驗以及以參數弱化的方式使用PFC3D進行數值模擬，探討降雨對逆向坡破壞的影響。試驗結果顯示降雨會縮短高傾角逆向坡發生撓曲傾覆破壞的時間，但對於潛在破壞面的發展位置無太大影響，試驗結果中，坡面產狀並無觀察到和現地場址所見到的潛在破壞面上方的材料崩壞掉落。 對照物理試驗結果，使用PFC3D模擬和試驗相同的重力場及配置，利用兩階段參數弱化模擬試體受到降雨弱化，其結果與物理試驗相較顯示，潛在破壞面斜率較物理試驗結果較陡，而在1g重力場下潛在破壞面發展位置則和物理試驗相同。 ;Taiwan locates in the Circum-Pacific Seismic Belt. Frequent seismic activities lead to Taiwan’s mountainous terrain and less plains. There are many typhoons that make landfall in Taiwan and these events result in heavy rainfall. Because of these reasons, the slope becomes unstable. The slope failure may be a threat to the residents near the hills and infrastructure. In order to discuss the failure mechanism of anti-dip slopes due to the effect of gravity, Hu (2019) performed the centrifuge tests and applied PFC3D to simulate the physical models. The results indicate that with thinner rock layer thickness and longer unsupported rock layer lengths, the anti-dip slope could deform and topple more easily. Zheng (2019) did the centrifuge tests and numerical simulation using the same model as Hu (2019) but with a second orthogonal joint set to discuss the effect of second joint set in the anti-dip slopes. The results showed that when the slenderness ratio of the layer is large, the failure mode is flexural toppling. The block toppling could occur with a smaller slenderness ratio. In this study, we designed the rainfall system in the centrifuge model to study the effect of rainfall to the anti-dip slopes. Meanwhile, PFC3D was also performed to investigate the equivalent effect of heavier rainfall to the anti-dip slopes. In order to simulate the deteriorating strength of rock layer subject to rainfall, we adopted two-step decreasing of the micro-parameters. The simulated results indicate that the rainfall could shorten the time to slope failure, however, the rainfall intensity doesn’t have much impact on the potential failure surface pattern. Comparing with the results of the physical tests, the numerical simulation in high gravity cannot have good result. In high gravity field of the numerical model, the potential failure surface of the model is steeper than that of the physical test in high gravity field. The potential failure surface’s position in high gravity field is the same as the physical test in 1g gravity.
