The Evolution of a Paleolandslide and the Formation of Resulting Colluvium - The Luchang Case Study.
|關鍵字:||古崩塌地;高山階地;地形演育;大規模崩塌;數值模擬;PFC;Paleolandslide;Alpine terrace;Geomorphological evolution;Large-scale landslide;Numerical simulation;PFC|
A large-scale landslide may occur in a sudden and result in devastating consequences with huge casualties and/or property loss. The study on the cause and effect of paleo-landslides may help to understand the principles of a landslide failure and its results. The important and relevant information about a paleolandslide is often not available or not complete; for example, the original topography of a studied paleolandslide is usually unknown. This research aims to investigate the geomorphological evolution of a paleo-landslide in Taiwan. A paleolandslide site in Luchang (in Miaoli County, Taiwan) is taken as a case study; special geological/geomorphological features including very thick (>100m) colluvium, steep scarps and alpine terrace landscape are clearly observable in this site. The objectives of this thesis study are threefold: to study (1) the origin of the very thick colluvium, (2) the geomorphological evolution of the paleolandslide, and (3) the formation of alpine terrace landscape. As a beginning, this research constructs the geological model of the site. Subsequently, the study proposes a conceptual model to explain the geomorphological evolution of the paleolandslide and the formation of the very thick colluvium. To support the reasonability of the proposed conceptual evolution model, the study adopts the software SLIDE to conduct slope stability analysis and uses the software PFC to carry out run-out simulation after landslide failure. The simulated result is compared with the current topography in this site. The conceptual model of geomorphological evolution is iteratively revised until the simulated results of the relict slope and the deposition after landslides eventually agree with the current topography. It is concluded that the deposited colluvium as a result of the west-to-east landslide can only provide one third of the actual colluvium at most. The main source of the very thick colluvium should come from the mass of the south-to-north landslide. The simulated results support that the south-to-north landslide is able to produce a 100-m colluvium; the results also indicate that the alpine terrace landscape was likely formed by retrogression landslide failure.
|Appears in Collections:||Thesis|