2009年8月8日,莫拉克颱風侵襲台灣,於中南部降雨最鉅,高雄部分區域降雨量超過2,000毫米。此一極端降雨情況下,8日發生小林村後方獻肚山邊坡之崩塌,造成超過400人罹難之慘劇;崩塌土方量高達2,500萬立方米之小林崩塌至今機制並未明確,因此本研究旨在提出完善分析了解小林崩塌之力學機制,並能夠詳盡演算水位、甲仙斷層不透水性質對此岩石邊坡破壞案例之影響。 為了解小林崩塌地質背景,參考中央地調所出版之地質圖(宋國城等,2000)以及李錫堤等(2009)、Chigira(2011)、林慶偉等(2012)所出版之新測地質圖資,推測小林崩塌為楔形破壞模式,但未有完整證據支持本論點,多以現地量測之少數位態決定。本研究以三維地形判釋、PIV質點影像測速法、現地位態、坡向坡度等資料進行統計,並繪製玫瑰圖、大圓投影圖加以佐證小林村崩塌之破壞模式是否符合楔形破壞準則,並進行獻肚山崩塌區域之地質調查,進一步由地質背景推斷為糖恩山砂岩、甲仙斷層主控破壞,並根據學者Evert Hoek及John Bray之楔形破壞演算分析破壞時之力學狀態。 確立小林村獻肚山邊坡崩塌之破壞機制後,將假定滲流水位面,深入演算水位面對邊坡安全係數之影響,以及甲仙斷層之不透水性與整體崩塌料源區穩定性之關係,針對莫拉克颱風之極端降雨狀況下對獻肚山岩坡料源區域進行分析,以期能夠充分了解小林村受降雨影響之崩塌機制;最後透過寬頻地震測站之震動訊號比對崩塌歷程及穩定性分析結果。
Typhoon Morakot hit Taiwan on 8 Aug. 2009 and brought over 2,000 mm accumulated rainfall in southern Taiwan. Under this extreme rainfall condition, Shiaolin Landslide occurred in the early morning on 9 Aug. 2009. The landslide volume of Shiaolin Landslide is about 25 million m3 and caused over 400 victims in Shiaolin Village. This research will identify failure mechanism and conduct stability analysis of Shiaolin Landslide and possible critical condition. To understand the mechanism of Shiaolin Landslide, the 3D topographic analysis, PIV analysis, slope & aspect analysis and attitude analysis were conducted, and comparisons of results were made to identify the failure type of Shiaolin Landslide. Meanwhile, the Shialin field investigation provided evidences for interpretation of the failure type of landslide. After the failure type is confirmed, the stability analysis were conducted. The seepage water table of the slope, the effects of ground water change induced by fault gauge, and the strength reduction of rock mass were considered in the detailed analysis. The results suggested that Shiaolin Landslide was a wedge failure controlled event. Stability of slope were analyzed to understand the critical state of Shiaolin Landslide in various conditions of ground water table and strength reduction of rock mass.