Case study of large-scale levee failures induced by cyclic softening of clay during the 2016 Meinong earthquake

Abstract

The 2016 Meinong earthquake (Meinong EQ) caused a serious disaster, including many liquefaction-induced damages, in southern Taiwan. This study investigated the “flow-like” failure of Rixin levee during the Meinong EQ through field exploration, laboratory test, and numerical analysis. The failure mechanism of soil liquefaction, however, failed to explain the case of Rixin levee because the levee foundation where the failure occurred was primarily composed of clayey soil. Therefore, the cyclic softening of clayey soil subjected to ground shaking was considered a key factor that induced the damage. Site characterization, liquefaction analysis, seepage analysis, slope stability analysis, and dynamic analysis indicated that when the strength reduction of Rixin levee (approximately 10%–15%) due to cyclic softening was accounted for during the 2016 Meinong EQ, the displacement of the embankment estimated using the Newmark sliding block method and finite element method was in line with the observed damage of the levee. The analysis procedure was validated with the case of the 2010 Jiasian earthquake, in which no failure occurred at the site under similar shaking.