Evaluation of an enhanced FS method for finding the initiation time of earthquake-induced landslides

In this paper, an examination of an enhanced FS method used for finding the initiation time of earthquake-induced landslides is presented. Validation was conducted via comparisons between the predicted and reported results of a benchmark site subjected to two major earthquake events: at Chi-Chi in 1999 (7.6 M_w) and Meinong in 2016 (6.4 M_w). To further validate the applicability of the ground motions utilized in this study, a finite element analysis was also carried out. Based on the results, satisfactory agreement between the predictions obtained by the enhanced FS method and the observed results in terms of the landslide initiation time was realized. Conclusions drawn from the study show that (a) the enhanced FS method can be both efficient and practical in finding the likely initiation time of a landslide, and it was found that the initiation time of the Tsaoling landslide during the Chi-Chi earthquake lay between 37.5 and 38.5 s; (b) when validating the enhanced FS method, the friction angle of 38.5^o obtained from direct shear tests rather than a smaller value of 20.8^o obtained from rotary-shear high-velocity friction experiments, led to a more appropriate results; and (c) the failure surface obtained by finite element codes was satisfactory when compared to the observed result.