Dynamic discrete analysis of an earthquake-induced large-scale landslide

The Chiu-fen-erh-shan landslide, estimated to have a volume of 36 million cubic meters, was triggered by the Mw 7.6 Taiwan Chi-Chi earthquake of 1999. The debris covered an area of 1.95 km2 and claimed 36 lives. During the sliding, the landslide mass disintegrated with its debris acquiring high speeds to reach over 1 km of travel distance. The main objectives of the study were to investigate if it was possible to numerically model the landslide progression, including slope disintegration, and to reproduce the post-failure configuration. Toward these goals, the study employed a discrete element method called discontinuous deformation analysis for the dynamic analysis. By incorporating the spacing and orientation information of the joints and bedding planes, the slope was modeled as an assemblage of discrete deformable blocks. Horizontal and vertical ground motions were simultaneously applied. The near-field digital strong records were affected by the large uplift of the hanging wall of the reverse thrust fault and corrections were made to address this issue. The study showed that the methodology adopted was able to capture essential characteristics of the landslide and gave a post-failure configuration resembling that observed in the field.