以遙測影像與數值模擬分析油車寮地滑之特性

Abstract

在西元2009年8月6日，莫拉克颱風襲擊台灣並引發許多山崩災害，其中包括位於嘉義縣梅山鄉油車寮聚落的油車寮地滑。根據災前與災後的相關研究，油車寮聚落附近的邊坡沿坡面發生數十公尺的位移，被認為是大規模崩塌發生的潛在區域。在本研究中，為釐清油車寮地滑的山崩機制，將應用質點影像測速(PIV)分析於兩對影像對中，並針對油車寮地滑的二維剖面模型進行有限元素法之數值模擬。 PIV結果顯示，油車寮地滑被觸發後主要向南滑動。崩塌塊體平均水平移動距離為40 公尺，最大滑移量為60公尺。然而，因地表覆蓋發生劇烈變化，以及PIV分析時搜尋窗格範圍過大，致使結果仍較不精確。 數值模擬結果中，由均質岩石或多層岩層組成的坡體均較滑動面已發育的坡體穩定。並且，以地表速度搭配數值模擬對潛在滑動面進行判釋的結果，雖能粗略推得滑動面形貌與深度，但與真實情形仍有出入。考量到地表下變形的機制，以此方法推估潛在滑動面可再搭配其他方法以精進。

In August, 2009, the Typhoon Morakot hit Taiwan and induced many landslide hazards. An induced landslide event happened near the Yucheliao settlement, Meishan town, Chiayi county, Taiwan. According to data and research after Typhoon Morakot, slopes near Yucheliao are considered as potential region for deep-seated landslide. In this study, the characteristics of the Yucheliao Landslide event is examined with the particle image velocimetry (PIV) analysis and numerical simulation. The PIV results show that the landslide block slipped southwardly after triggered. The block slip is 40 m averagely in horizontal distance, and the maximum slip is 60 m. However, the inaccuracy of the results occurs in the PIV analysis due to severe change in land cover and large interrogation window size. From the numerical simulation, it is estimated that both the slope with homogeneous rock and slope with layered rock are more stable than the slope with pre-existing slip surface. The slip surface could be roughly interpreted by surface displacement with numerical modeling, but the depth and geometry have obvious differences from real situation. By considering the underground deformation of the landslide, the accuracy of interpreting potential slip surface could be improved when other approaches are applied.