Analysis of Liquefaction Susceptibility in the Nakdonggang Delta Region via Effective Stress Analysis

During the 2017 M5.4 Pohang earthquake, significant damage occurred because of liquefaction. However, South Korea is located in a stable continental region where earthquakes are rare, and the widely-used simplified liquefaction assessment methods have not been validated domestically. Hence, this study evaluates liquefaction at several locations in the Nakdonggang Delta region via effective stress analysis and compares the results with those of the simplified method of Boulanger and Idriss (2008). For the liquefaction assessment, a hypothetical earthquake scenario with a magnitude of 6.2 on the Dongnae Fault was assumed, and ground motions were generated via broadband hybrid ground motion simulation. The effective stress analysis was performed using OpenSeesPY and a multi-yield plasticity model. The results of the liquefaction assessment revealed significant differences between the two methods. The simplified method indicated that shallow sediments in the Nakdonggang Delta region were more susceptible to liquefaction, whereas the effective stress analysis indicated that loose, shallow sediments were more vulnerable. These results suggest that simplified liquefaction assessment methods must be carefully validated for application in South Korea. Future studies will need to accurately reflect dynamic soil properties based on experimental data to help validate effective stress analysis methods and assess the applicability of simplified methods for practical application in South Korea.