應用三維離散元素法分析潛在性山崩-以廬山溫泉北坡為例

台灣位於歐亞大陸板塊與菲律賓海板塊交界處，為全世界最活耀的造山帶之一，因此，抬升及侵蝕速率驚人，且地震頻繁，再加上每年平均4個颱風侵襲，山區極易發生大規模的山崩事件。本研究將不同於以往，過去研究著重於重建與分析已發生之山崩事件的過程與運動模式，我們將應用以離散元素法(Discrete Element Method,簡稱DEM)為基礎所開發的三維顆粒流軟體PFC3D於山崩災害潛勢區域。廬山岩體滑動區為國內具有重大山崩災害潛勢之地區之一，位於南投縣仁愛鄉精英村廬山溫泉區北坡，為一具有高傾角的深層岩體潛移區，近十年來，每逢豪雨便可紀錄到滑動現象，並伴隨著道路破壞、房屋變形等損壞跡象，因此，在此研究中，我們將以廬山岩體滑動區為例，運用廬山溫泉區北坡歷年來傾度管與時域反射儀的監測資料，推估出可能滑動面的範圍及深度，境況模擬若發生山崩的過程與運動型態，並探討在不同邊界條件下，顆粒之堆積範圍及可能危害之保全對象。模擬結果中顯示，整個廬山溫泉區將在20秒內被土石覆蓋，僅有東邊有少數房屋倖存，但仍須考慮堰塞湖可能造成之威脅。堰塞湖的形成將可能會淹沒政府對於廬山溫泉區所定義的緊急避難處所-廬山警光山莊。顆粒的最大滑移速度依據不同大小範圍的山崩模擬，分別可高達每秒35 公尺與55 公尺，並對約40公頃與50公頃的區域造成影響。從監測滑移面未延伸至下半部坡體的模擬變形資料中，可對應到實際傾度管所監測到的變形曲線，因此，若滑移面繼續向坡趾處延伸，在極端氣候等因素影響下，不能排出發生巨變型山崩的可能性。本研究藉由三維數值模擬的方式，了解未來若發生山崩，其運動型態、速度與堆積形貌，並可以考量到山崩的側向影響範圍，將能做為未來山崩衝擊區域的災害評估，提供政府單位對山崩潛勢性高之區域土地規劃的重要參考。

關鍵字

山崩；廬山溫泉區；近況模擬；三維離散元素法；敏感區域

並列摘要

Landslide is a pestilent natural disaster in many countries around the world. Due to the subtropical climate with annual average four typhoons, combined with frequent earthquakes facilitate to the gravitational sliding in Taiwan. The potential Lushan landslide area is located at a famous hot spring district of Nantou County in central Taiwan which slides frequently due to heavy rainfall. Lushan landslide area demonstrates a possible deep-seated (up to 108 meters) creep along a dip-slope direction with high dip angle. In this study, we simulate the possible scenarios of catastrophic landslide, kinematic process and the assessment of impact area by 3D Particle Flow Code (PFC3D), which is conducted by the three dimension granular discrete element method. The sliding surface is extrapolated by the results of inclinometer and Time Domain Reflectometer (TDR) monitoring systems. Considering the complex geological background of possible different sliding surfaces to estimate the impact area after landslide for pre-landslide scenario simulations, we performed numerical experiments with different boundary conditions and parameters. From our numerical experiments, the Lushan hot spring district is predicted to be covered in 20 seconds except some buildings on the eastern side, where still be menaced by avalanche lakes including the secure refuge of Lushan hot spring district. The predicted maximum velocity is about 35 - 55 m/s and destroy an area about 40 - 50 hectares. The deformation tendency of models without lower sliding surface is similar to the records of inclinometers. From the simulations, when sliding surface extending to the lower slope, that may cause catastrophic disaster in the future. The numerical results of this study will suggest important assessment of movement and deposition for potential landslide cases and landslide susceptibility mapping.

並列關鍵字

Landslide ； Lushan ； Scenario simulation ； PFC3D ； Susceptibility map

參考文獻

Campbell, C. S. (1989), Self-lubrication for long runout landslides, J. Geol., 97, 653-665.

Campell, C. S., and C. E. Bernnen (1985), Chute flows of granular material: Some computer simulations, J. Appl. Mech., 52,172-177.

Cao, J., G. Ahamdi, and M. Massoudi (1996), Gravity granular flows of slightly frictional particles down an inclined bumpy chute, J. Fluid Mech., 316, 197-221.

Chang, K.-J., and A. Taboada (2009), Discrete element simulation of the Jiufengershan rock-and-soil avalanche triggered by the 1999 Chi-Chi Earthquake, Taiwan, J. Geophys. Res., 114, F03003, doi:10.1029/2008JF001075.

Chigira, M. (1992), Long-term gravitational deformation of rocks by mass rock creep, Eng. Geol., 32, 157-184.

國際替代計量

應用三維離散元素法分析潛在性山崩-以廬山溫泉北坡為例

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