地質構造與大型崩塌之關係－以阿里山公路為例

On the Relationship between Geological Structures and Mechanisms of Large Landslides in the A-Li Mountain Highway, Taiwan

黃筱婷(Hsiao-Ting Huang) ； 楊哲銘(Che-Ming Yang) ； 曹孟真(Meng-Zhen Cao) ； 董家鈞(Jia-Jyun Dong) ； 劉家男(Chia-Nan Liu) ； 王泰典(Tai-Tien Wang) ； 李維峰(Wei-Feng Lee) ； 謝有忠(Yu-Chung Hsieh)

《中華水土保持學報》 42卷4期 (2011/12) Pp. 279-290

https://doi.org/10.29417/JCSWC.201112_42(4).0002

摘要

邊坡滑動除與降雨、地震以及人為因素等誘因外，地質構造如層面、節理系統、褶皺、斷層等，均直接或間接影響邊坡的穩定性。因此，詳細野外地質調查與構造判釋對山崩機制研判相當重要。為了解地質構造與邊坡破壞之相關性，本研究針對阿里山公路（台18線）隙頂至石桌之間沿線進行地表地質調查以及地形、構造分析，並選定公路上、下邊坡之崩塌地，為重點調查區域。經航照判釋、野外調查、層面與不連續面位態統計以及構造分析，本研究於1／5000比例尺之地形圖標示出影響山崩之褶皺構造，並決定其傾沒方向，藉由地質構造調查與山崩圈繪成果，本研究說明地質構造如何控制研究區多處山崩之破壞機制。結果顯示研究區受構造控制之大型山崩共分四類：（a）熨斗狀地形受層面與節理控制之岩楔破壞；（b）褶皺軸部通過、地層破碎而重複發生之岩屑崩移；（c）緊密褶皺、層面呈曲面狀而滑動規模受限之非典型順向坡滑動；（d）向斜與背斜構造間受褶皺軸傾沒方向與傾角控制之平面型滑動。綜而言之，邊坡穩定與否受構造及地形影響甚巨，大型山崩潛勢分析應審慎考量構造因素。

關鍵字

邊坡 ； 破壞機制 ； 地質構造 ； 順向坡

並列摘要

In order to find the relationship between geological structures and mechanisms of large landslides, a field investigation of topography, geology, and geological structures between Shi-zhou and Xi-ding was conducted along the Ali Mountain highway (T18 route) where landslides are triggered frequently. The aerial photos of the study area after Typhoon Morakot were interpreted to recognize landslides which were later verified in the field to form a landslide map. The characteristics of structures, such as orientations of discontinuities and vectors of fold axes, were identified from aerial photo interpretation and field investigation. Accordingly, the identified folds axes and fold plunges, which would influence the mechanisms of landslides, were marked on a 1/5000 geology map. Through interpreting the landslide map and the 1/5000 geology map, four landslide patterns which were strongly correlated with geological structures were observed: (1) wedge failure in iron shape topography is controlled by bedding and joints; (2) fragmented landslides usually occur in the vicinity of a fold axis; (3) for untypical dipslope failure, the occurrence and the scale are dominated by series of tightly spaced folds; (4) translational landslides are controlled by the vector of the fold axis. In conclusion, the geological structures and topography significantly control the mechanisms of large landslides.

並列關鍵字

Slope ； Failure Mechanism ； Geological Structure ； Dip Slope