Simulating the postfailure behavior of the seismically- triggered Chiu-fen-erh-shan landslide using 3DEC

Abstract

The dip-slope Chiu-fen-erh-shan landslide, estimated to have a volume of 36 × 106 m3, was triggered by the Mw 7.6 Chi-Chi earthquake. The debris covered an area of 1.95 km2 and claimed 36 lives. Although different discrete element methods have been applied to simulate the postfailure behavior of the Chiu-fen-erh-shan landslide in the last two decades, the lateral and dip-slope rock movements, the impact of the sliding debris against the hill in front of the slope toe and its final deposition have not been fully simulated. The major objective of this study was to investigate the possibility of applying three-dimensional (3D) numerical modeling code 3DEC to numerically model the debris movement and deposition of the Chiu-fen-erh-shan landslide under the impact of the Chi-Chi earthquake. By incorporating the spacing and orientation information of the joints and bedding planes, the slope was modeled as an assemblage of polyhedrons. Seismic ground motions were simultaneously applied in three dimensions. The shoveling effect was considered to erode the hill in front of the slope toe so as to extend the impact area and match more closely actual depositional topography. This study showed that the 3DEC simulations captured essential 3D characteristics of the landslide and resulted in a postfailure configuration similar to that observed in the field.