Tieliku landslide, northern Taiwan: Possible role of focused bedrock exfiltration tested using a laboratory analogue

本論文研究位於北臺灣的雪山山脈鐵立庫崩塌地崩塌過程及破壞之原因。研 究方法分爲兩個部分：野外量測及實驗室模型分析，最後應用這兩個部分所產生 的結果解釋鐵立庫崩塌情形。 野外量測包含地表測量，航照分析，地形分析及樹木年輪分析。實驗室應用 小山坡模型量測不同地下水來源及岩盤地形對於山坡破壞之過程，並透過影像分 析進行量測. 經由野外量測及實驗室模型分析的比較之後，結果顯示鐵立庫崩塌 地的崩塌過程有可能是由鐵立庫山坡最上方的岩盤湧水所造成的局部高水壓所 控制的。How does focused bedrock exfiltration influence the failure process of a hillslope? If a hillslope has already begun to fail, what features of the failure or the hillslope can be used to distinguish between a failure process controlled by rainfall and a failure process controlled by a point source of bedrock water? These questions play a key role in the investigation of a landslide located in the north central mountains of Taiwan, known as Tieliku. The Tieliku slope failure is hypothesized to have been influenced by high pore water pressures caused by a focused source of bedrock water exfiltration. Research of Tieliku is conducted using field and laboratory techniques. First the history of the slope failure is documented using aerial photographs, survey measurements, high resolution air LIDAR measurements and slope movement data collected from annual rings of trees growing along the upper edge of the scarp. Second, a laboratory analogue hillslope model is used to test hypotheses regarding soil water, bedrock topography and landslides. Results of the analogue model tests are quantified via detailed topography measurements and sediment production histories generated using image analysis techniques. In total, six different experiments are performed and contrasted. Through comparison of Tieliku field data to experiment results, several lines of evidence are found to support the hypothesis that the Tieliku slope failure was influenced by localized, high pore pressures at the top of the failure scarp. In the experiments, localized high pore pressures result from flow exiting a buried pipe. At Tieliku, elevated pore pressures may be caused by focused bedrock exfiltration