Simulation for the Evolution of a Large Scale landslide－The Jiasian Case as an Example.
|關鍵字:||地形衍育;概念模型;河道下切;大規模崩塌;數值模擬;PFC3D;Geomorphological evolution;Conceptual model;Channel incision;Large-scale landslide;Numerical simulation;PFC3D|
A large-scale landslide may fail in a sudden and result in devastating consequences. The hillslope of a potential large-scale landslide could experience a series of geomorphological evolution in the past. The geomorphological evolution may be resulted from previous landslides followed and their runout. By exploring the past geomorphological evolution of a potential large-scale landslide site, it will not only be beneficial to better understand the site condition at present, but also help to predict the possible instability of the slope in the future. This thesis aims to develop a method for exploring the conceptual geomorphology-evolution model of a site with large-scale landslide potential. The method starts with finding a reference hillslope adjacent to the site with potential of large-scale landslide. The reference hillslope should have similar geology and geohydrology conditions with the studied site with potential large-scale landslide. Next, possible conceptual model for geomorphological evolution is nominated and checked whether the model is admissible in kinematics. The admissible conceptual model then is examined by using the limit equilibrium method and run-out simulation; this process can be conducted stage by stage, if the geomorphological evolution contains several evolution phases. Each evolution phase is simulated successively for a scenario of heavy rainfall or earthquake as a triggering factor. With the aforementioned method, a slope site in the Jiasian district, Taiwan was taken as a case study for studying the geomorphological evolution of a hillslope with large-scale landslide potential. A conceptual model was proposed to explain the geomorphological evolution of this slope. The landform of this hillslope was originally in a convex-concave form. A large-scale plane failure on the upper slope took place probably triggered by either a heavy rainfall or a large earthquake. The sliding mass moved down and deposited in the downslope region; the colluvium covered the downslope area all the way toward the toe of the slope. Afterwards, the channel incision of the Qishan River by the toe of the hillslope gradually developed; river bank scouring was also in progress. The incision and bank scouring resulted in several local slope failures in the lower part of the slope. Consequently, the hillslope gradually turned into its current appearance after experiencing these landform-change phases. The slope stability of this site was further assessed according to the simulated results from the conceptual model. The likelihood of the recurrence of a large-scale landslide in the future is relatively low.
|Appears in Collections:||Thesis|