- 學位論文
投89線道15.85K的破壞歷程及臨界雨量探討
Collapsed Squence and Critical Rainfall at 15.85K of Nantou 89 th County Road
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摘要
近年來氣候變遷，極端降雨事件漸增，引起台灣各地崩塌、地滑、土石流等災害。本研究區域投89線道，為南投縣仁愛鄉的一條交通要道，因屢次遭受颱風豪雨的摧殘，加上野溪的侵蝕更是誘發道路沿線大面積的崩塌，本研究主要探討投89線道15.85K的破壞歷程及臨界雨量，期望以此做為防災、治災及疏散之參考，保障人民的生民財產安全。 本研究利用2001年至2013年期間15.85K的歷史資料及航照圖，包含正射影像、彩色航空影像、Google Earth影像進行破壞事件前後的比對，整理出其破壞歷程，下邊坡鄰野溪之崩塌地，因侵蝕先行產生破壞，上邊坡崩塌地因豪雨及下邊坡不穩，接續產生滑動及崩塌，道路也一再往上邊坡改道通行，共可整理出有7處不同位置的崩滑面。 同時對15.85K有造成破壞及沒造成破壞影響之降雨事件，使用單場累積降雨量、最大24hr雨量及I-T型降雨警戒模式進行雨量比較，得到對15.85K造成破壞之事件其臨界雨量約為270mm，接著利用SEEP/W及SLOPE/W分析二個剖面，並代入莫拉克降雨條件得出，安全係數均會隨著降雨而逐漸下降，且滑動位置皆位於道路上邊坡處。而在同樣的降雨時間，地下水位的高度越高，安全係數越低，地下水位的高度越低，安全係數則越高。
並列摘要
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.
參考文獻
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