Collapsed Squence and Critical Rainfall at 15.85K of Nantou 89 th County Road

• Main Authors: Yi-Chun Yeh, 葉怡君
• Other Authors: Sung-Chi Hsu
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/46005160056309723624

碩士 === 朝陽科技大學 === 營建工程系 === 104 === In recent years, chances of extreme heavy rain have increased due to climate change, which resulting in disasters such as collapses, slope failures and mudslides in Taiwan. The research focuses on Nantou 89th Country Road, which is one of the main roads located at Ren-ai Township, Nantou Country. Invaded by typhoon, heavy rain, and torrent, several locations of Nantou 89th Country Road had collapsed. The research will discuss the collapsing history and failure processes at 15.85K of Nantou 89th country road and obtain the critical rainfall. Thus, the results hope to provide an insight into disaster prevention, solution and evacuation in order to protect inhabitants’ safety. The research retrieved the history data and aerial photos of 15.85K from 2001 to 2013, including orthophotos, colorful photographic images and Google Earth images. The areas of failures and failure processes are revealed by comparing former and after images. The landslide of lower side slope near the gully had been eroded first and caused upper slope to slide later. Thus, the upper side slope slid and collapsed due to heavy rain and unstable lower side slope. As a result, the road path has been forced changing to upper side slope in order to keep it trafficable. There are totally 7 landslides in different locations. The research compares the rain incidents, which caused failure or non-failure of a slope, at Nantou 89th Country Road in many aspects. The cumulated rainfall from single incident, maximum cumulated rainfall within 24 hours, and I-T type raining alarm are compared. The results show that critical rainfall causes damage is about 270 mm. SEEP/W and SLOPE/W are used to simulate two slope profiles experienced the rainfall incident of Typhon Morakot. The factor of safety decreases as the increase of cumulated rainfall. The possible sliding planes are both located at the upper slope above the road. At the same raining duration and intensity, the higher initial ground water level, the lower the safety factor, and vice versa.