Pseudostatic analysis of Tsao-Ling rockslide caused by Chi-Chi earthquake

During the 1999 Chi-Chi earthquake, extensive slope failures were triggered by the earthquake in central Taiwan. Among those, a large-scale dip-slope slide in Tsao-Ling occurred, which involved the mass movement of 120 million cubic meters. Four catastrophic dip-slope rockslide events in history in Tsao-Ling are reported; furthermore, the stability analysis of the Tsao-Ling landslide caused by the Chi-Chi earthquake was conducted for the original and remaining slope. Results of pseudostatic analysis indicated that a reduction factor of 2/3 for both vertical and horizontal peak ground acceleration with 30% of material strength degradation were likely the case for inducing the Tsao-Ling landslide, and the effects of vertical acceleration were significant. Accordingly, it was concluded that ground motion and degradation of material strength were the major factors for the inducement of the Tsao-Ling landslide by the Chi-Chi earthquake.