Centrifuge Modeling of Soil Liquefaction Triggering: 2017 Pohang Earthquake

Abstract

Soil liquefaction by earthquake results in significant soil deformation and can cause substantial damage to infrastructure. Accordingly, there is a critical need to analyze earthquake case histories, and such analysis should focus on elucidating ground motion characteristics and field measurement data associated with instances of soil. The most straightforward approach to identifying liquefaction triggering involves examining pore water pressure records, which is challenging in many susceptible areas due to the absence of installed pore water pressure transducers. Therefore, evaluating liquefaction commonly relies on surficial evidence, such as sand boil or lateral spreading. However, this evaluation can miss the liquefaction triggered case without such surficial evidence. This study modeled the 2017 Pohang liquefaction, a first-time occurrence in South Korea, through a centrifuge test replicating the liquefied site based on field investigations, including borehole tests and recorded earthquake motions. We comprehensively assessed liquefaction using the ratio of excess pore water pressure alongside analyses of acceleration time histories, shear stress-strain hysteresis, and time-frequency histories. These results were compared with a conventional method that overlooked pore water pressure, leading to overestimation. Furthermore, using a simplified method, we compared liquefaction triggering evaluation results from the centrifuge cone penetration test and on-site standard penetration test. This, along with the factor of safety, substantiated the validity of the centrifuge results.