Effects of strength properties of discontinuities on the unstable lower slope in the Chiu-fen-erh-shan landslide, Taiwan

Abstract

The Chiu-fen-erh-shan landslide was a huge dip-slope avalanche triggered by the devastating Chi-Chi earthquake in central Taiwan in 1999. Anomalous geomorphic precursors, such as ground subsidence and thrust, which are signs of slope instability, were subsequently observed on the lower slope of the Chiu-fen-erh-shan landslide in November, 2002. Post-failure behavior and affected area of the lower part of the landslide must be investigated to provide adequate countermeasures. This study presents the results of the post-failure behavior simulation of the lower slope of the Chiu-fen-erh-shan landslide using Discontinuous Deformation Analysis (DDA). The simulation results show that the surface rocks in the sliding mass move faster and further than the rocks at great depth. The angle of internal friction is found to have a great influence on the failure process than does the cohesion. The sliding rocks are accumulated in the depression in front of the toe of the landslide except under the conditions of very low internal friction. The depression performs as a buffer zone when the lower slope fails.