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Abstract: This paper is aimed at creating an empirical model for assessing failure potential of highway slopes, with a special attention to the failure characteristics of the highway slopes in the Alishan, Taiwan area prior to, and post, the 1999 Chi-Chi, Taiwan earthquake. The basis of the study is a large database of 955 slope records from four highways in the Alishan area. Artificial neural network (ANN) is utilized to “learn” from this database. The developed ANN model is then used to study the effect of the Chi-Chi earthquake on the slope failure characteristics in the Alishan area. Significant changes in the degrees of influence of several factors (variables) are found and possible reasons for such changes are discussed. The novelty of this paper lies in the fact that the developed ANN models are used as a tool to investigate the slope failure characteristics before and after the Chi-Chi earthquake. [Copyright &y& Elsevier]

Earthquakes can generate seismic disturbances that propagate vast distances and trigger landslides that can achieve high-speeds. It remains difficult to identify the co-seismic ground motion of these landslides and their triggering earthquakes. In this paper, we report on the analysis of co-seismic ground motions generated by the initiating fracture and deposition impact of the Tsaoling landslide. The landslide, with a source volume of 125 × 10 6 m 3 , was triggered by the 1999 Chi-Chi earthquake in Taiwan. The ground motion was recorded by a strong ground motion station, CHY080, near the scar area. The polarization of the seismic waves indicates that the peak acceleration was parallel to the dip direction. Modified ensemble empirical mode decomposition (EEMD), with additional clustering analysis, was applied to decompose the seismic signals. Two instances were found in the seismic records of a series of peculiar wave packets, with the first being associated with the landslide initiation and the second the landslide impact on the deposit valley. To confirm the first landslide breakage, the decomposed signals were compared with the predictions of the analytic elastic wave model and Newmark analysis. The landslide impact was verified with a computational fluid dynamic simulation. Comparison between the EEMD decomposed signals, elastic wave theory, Newmark rigid body analysis, and numerical simulation demonstrates the claimed landslide motion. [ABSTRACT FROM AUTHOR]

Abstract: The 1999 Chi-Chi earthquake triggered the catastrophic Tsaoling landslide in Taiwan. The geomorphological change measured from the data of the 1989 and 2000 aerial photos reveals that the scar and deposit volumes are about 0.126 km3 and 0.15 km3 respectively. The debris material ran over a distance of 1.6 km with 500 m descent in elevation. In this paper, we use the continuum model of hydraulic flow, SHALTOP2D, based on the equations of Bouchut and Westdickenberg to simulate numerically the landslide dynamics. When the mass is moving, the flow is assumed hydrostatic with a basal Coulomb friction. The best fit is obtained using the basal friction angle equal to 6°, the only parameter of the simulation, uniformly applied in the calculation domain. The landslide front reaches the Chinshui river valley, the foothill of the slope, within only about 25 s after initiation and the motion settles in about 113 s. The maximum speed is estimated 75 m/s. The spreading of the deposit agrees well with the field measurement. [Copyright &y& Elsevier]

Abstract: The Jiufengershan rock avalanche was one of the largest and most damaging landslides triggered by the Chi-Chi earthquake (M L =7.3, M W =7.6) of 21 September 1999. The rock avalanche transported a mass of sedimentary rock 50 m thick and 1.5 km long, located on the western limb of the Taanshan syncline. The surface of rupture coincides with the bedding plane and dips moderately toward the Jiutsaihu valley. This paper is mainly devoted to the study of post-seismic surface processes that affected the sliding surface as well as the debris deposit, from September 1999 to February 2003. Large fractured blocks and a debris layer observed on the surface of rupture were subjected to mass wasting processes and denudation. The quantification of erosion was made using two different approaches. First, the subpixel correlation method was used to determine the horizontal displacement field from aerial photographs taken, respectively, 2 and 3.5 months after the earthquake. Displacements ranging from 1 to 6 m were observed around unstable blocks located at the western flank of the surface of rupture. Second, the co-seismic and post-seismic volume distributions in the sliding zone were determined from three digital elevation models, including a LiDAR image taken in 2002. Post-seismic erosion and deposition from September 1999 to April 2002 were mainly associated with mass wasting and denudation at the surface of rupture, deposition in small basins and lakes located in the debris deposit, and evacuation of materials from the debris deposit along natural and artificial drainage channels. The vertical compaction is 1% of the initial height of the deposit. [Copyright &y& Elsevier]

The method by Iwasaki et al. [Iwasaki, T., Arakawa, T., Tokida, K., 1982. Simplified procedures for assessing soil liquefaction during earthquakes. Proceedings of the Conference on Soil Dynamics and Earthquake Engineering, Southampton, UK, pp. 925–939] for evaluating the liquefaction failure potential is widely used in Japan, Taiwan, and other countries due to its ease of use and general applicability. In this method, an index, called the Liquefaction Potential Index (IL), is calculated based on an integration of the calculated factor of safety (Fs) over depth with a weighting function. Iwasaki et al. (1982) provided a set of criteria to interpret the calculated index IL based on a calibration with his dataset of field performance cases. However, in their method, the factor of safety (Fs) is based on the liquefaction evaluation method adopted in the Japanese Highway Bridge Design Code [JSHE, 1990. Highway Bridge Design Guide Book. Japan Society of Highway Engineering, in Japanese]. Whether other liquefaction evaluation methods can be used in conjunction with the index IL or not needs further investigation. In this paper, the Cone Penetration Test (CPT) data from Yuanlin, Taiwan, the area that suffered the most from liquefaction in the 1999 Chi-Chi, Taiwan, earthquake, are analyzed. Three CPT-based methods are used for the calculation of the factor of safety for these cases derived from the Chi-Chi earthquake. These factors of safety are used to define the liquefaction potential and risk indexes. The calculated indexes are then used to construct the failure potential maps, and these maps are checked with the field observations. The study shows that the Liquefaction Risk Index (IR) defined in conjunction with the Juang et al. [Juang, C.H., Yuan, H., Lee, D.H., Lin, P.S., 2003. Simplified CPT-based method for evaluating liquefaction potential of soils. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, vol. 129, no. 1, pp. 66–80] method yields the best result in interpreting field observations. [Copyright &y& Elsevier]

This paper presents an update of the Hyperbolic Function (HBF) method to evaluate the liquefaction potential of sandy soils. The HBF method was created after the 1999 Chi-Chi, Taiwan Earthquake (M w = 7.6) using the database of case histories developed based on field observations and in situ and laboratory tests in areas affected by the 1999 event. The updated HBF method reported herein reflects the 20-year efforts of research and practice in Taiwan after the 1999 event. Here, the original database created by Hwang and his co-workers was first re-examined and updated. The updated Chi-Chi database was supplemented with the cases derived from the 2016 Meinong, Taiwan Earthquake, and some selected data from other parts of the world. This new database was then used to update the parameters of the HBF model through rigorous statistical methods. The HBF model is unbiased (as it corresponds to a probability of 50%). The updated HBF method, a deterministic model, is further extended into a probabilistic version through rigorous statistical calibration. This probabilistic version is expressed as a mapping function that relates the factor of safety (F S) against liquefaction to the probability of liquefaction (P L). The design recommendation for engineering practice in Taiwan is provided based on the calibrated P L - FS mapping function. The updated HBF method is demonstrated through examples to be an easy-to-use procedure for liquefaction potential evaluation. Use of Bayes' theorem for updating the liquefaction probability and the new concept of liquefaction likelihood ratio are also discussed. • An updated database of liquefaction and non-liquefaction cases from Taiwan is created. • An easy-to-use HBF model for liquefaction evaluation is presented, which emerged from two decades of research in Taiwan. • Procedures for the calibration of empirical models for liquefaction evaluation are introduced and illustrated. • The concept of the liquefaction likelihood ratio (LR) is presented with a graph of LR contour curves for Bayesian updating. [ABSTRACT FROM AUTHOR]