| Summary: | 碩士 === 國立中興大學 === 水土保持學系所 === 105 === The Lushan slope located in the Renai Township, Nantou County, has slid and disconnected the road due to typhoons for recent decades. It’s seriously affecting the Lushan Hot Springs Area and the property security of the local residents in the lower slope of Lushan Hot Springs Area. Therefore, Whether Lushan landslide area will eventually collapse or not is the problem many people want to know. This study built the numerical model by Plaxis 3D, and analyze the Lushan Landslide with respect to rainfall. The numerical model was validated by 69 Heavy Rainfall and Typhoon Morakot. After proving the effectiveness of the model by checking the observation data of the two rain events, we design 18 rainfall events and use them to analyse if Lushan landslide area will eventually collapse. These 18 rainfall events were 24hr, 48hr and 72hr rainfall duration with the rainfall of 5, 10, 25, 50, 100 and 200 years recurrence interval, respectively.
This model has been validated to reflect the current situation of the reality appropriately. This study shows the relationship between the displacement and rainfall in the landslide area. According to the results, the maximum displacement of Lushan landslide area occurs at the maximum rainfall intensity of the 18 rainfall events. And no matter which rainfall event, the first stage displacement occurs when the cumulative rainfall reaches 250mm. A big displacement will occurs due to heavy rainfall defined by Central Meteorological Bureau.
The Lushan landslide area will not collapse during these 18 rainfall events. Even the ground water is raised to the surface, it will not collapse. At last, the strength of the slope is reduced to cause collapse. The results show that when the cohesions of the landslide part and its lower slope drop to 95 and 105 kPa, the slope will collapse during 48hr rainfall duration with the rainfall of 200 years recurrence interval.
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