| Summary: | 碩士 === 國立成功大學 === 土木工程學系 === 104 === 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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