劇烈地震的發生通常容易帶來嚴重的災害，而地震是引發山崩的原因之一。2016年四月，日本熊本地區發生Mw7.3的地震主震，誘發了大規模的山崩，並破壞了阿蘇大橋。由數位高程模型(DEMs)掃描阿蘇橋山崩前後地貌變化，發現阿蘇橋山崩的山崩機制可能有兩種。本研究為了分析阿蘇橋山崩的破壞行為與初始時間，利用兩種分析方法：Newmark塊體滑動分析以及有限元素(FEA)數值模擬軟體PLAXIS-2D，來進行山崩初始時間以及山崩滑動面預測。

為了驗證研究方法的可行性，利用1999集集地震引發草嶺山崩的案例為驗證對象。由於草嶺山崩為台灣規模最大且紀錄最完整之山崩事件，過去已經有眾多學者進行相關數值分析與力學實驗研究。因此，本研究蒐集過去草嶺山崩研究成果並進行整理，並利用1999年集集地震及2016年美濃地震對草嶺山崩的影響進行山崩初始滑動時間及可能滑動面的比對。利用本研究方法得到草嶺山崩的時間t=37.5~40秒，破壞面位置與草嶺山崩實際上觀察到的破壞面吻合，因此符合過去研究結果，並已驗證了方法可行性。

再來，本研究將塊體滑動分析以及有限元素法應用於阿蘇橋山崩的初始時間與滑動面。本研究結果顯示：(1) 阿蘇橋山崩初始時間為18.45~21秒之間 (2) 利用FEA推測滑動面位置，岩土剪力強度參數ϕ=35°和c=80kPa時與DEMs觀察到的滑動面最類似 (3) 阿蘇橋山崩之地質為火成岩類，由FEA得出之岩土剪力強度比學者建議強度略低，其原因可能為風化所導致 (4) 由FEA結果發現滑動面集中在山脊間，因此山崩破壞機制推測為受到主震作用下直接崩落
本研究所提出之方法說明了Newmark塊體滑動分析和有限元素法能夠有效且合理的推測山崩初始時間以及破壞面。因此，將本研究方法利用MATLAB GUIs設計成方便使用的應用程式，並提供能夠快速推測山崩初始時間的程式，以便後續研究與應用。

本研究在進行FEA模擬並未考慮垂直地震加速度，因此利用擬靜態分析評估垂直地震加速度對山崩的影響，同時考慮進不同垂直地震加速度方向來進行邊坡穩定性的分析，以驗證忽略垂直加速度可能導致邊坡滑動面的預測產生誤差。

A catastrophic earthquake can easily result in destructive disasters. It is well-known that earthquakes are one of the causes of landslides. On April 16, 2016, the main-shock of the Kumamoto earthquakes (Mw7.3) struck beneath the Kumamoto City and generated large-scale landslides around the Aso area. Among the landslides, the Aso-bridge landslide is the largest one.

According to topographical scanning of Digital Elevation Models (DEMs), the collapse of the Aso-bridge could suffer from two mechanisms. To analyze the initiation-time and failure behavior of the Aso-bridge landslide, this study utilizes two approaches: the Newmark’s sliding block method and a finite element analysis (FEA) program-PLAXIS-2D.

In order to ensure our research methods are practicable, this study makes use of a famous case – the Tsaoling landslide induced by the Chi-Chi earthquake, for verification. The results of this study show the landslide time is t=37.5~40 sec, and the obtained failure surface is close to the actual observed surface. Therefore, the results fit-well with previous studies and are thus the verified approaches for the study. Furthermore, this study also uses the data of the 1999 Chi-Chi earthquake and the 2016 Meinong earthquake to conduct further verification of the approaches to analyze landslide behavior and potential failure surface of the Tsaoling landslide.

Upon the verifications, this study applies the verified approaches to analyze the landslide initiation-time and landslide failure surface of the Aso-bridge landslide. The results show that (i). The initiation-time of the Aso-bridge landslide is between 18.45~21sec. (ii). The geometrical strength parameters are ϕ=35° and c=80kPa, and the failure surface is close to the actual observed surface predicted by DEMs. (iii). The geology of Aso-bridge is Igneous. The soil strength is slightly less than the peak value of 95 kPa reported, suggesting that the strength of the soil layers was reduced likely due to weathering. (iv). The Aso-bridge landslide was excited immediately from the ridge of the slope when the main-shock of the Kumamoto earthquake struck.

The study demonstrates that the Newmark’s sliding method and the finite element analysis (FEA) can be applied to analyze the landslide initiation-time and the landslide failure surface with a reasonable agreement.

Finally, since the vertical acceleration is not taken into account in the FEA, a pseudo-static analysis is used to evaluate the effect of the landslide considering the vertical acceleration as to verify the errors in predicting the failure surfaces of the landslide. A MATLAB GUI, a user-friendly Apps, which is convenient for rapidly predict the landslide initiation-time, has also been developed to facilitate subsequent research and application.

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