Physics-inspired geophysical assessment of liquefaction potential in Pohang, South Korea

This study aims to assess the liquefaction potential of soil deposits where soil boiling and liquefaction have been first observed since the Pohang earthquake in 2017. We use multi-physics techniques for site characterizations and laboratory analysis for in situ soil samples. Depth-dependent engineering soil properties are analyzed using effective stress–depth models, where extensive datasets compiled from previous studies enhance data reliability. A physics-inspired and data-driven framework successfully establishes a lower bound for low plastic clay and upper bound for loose silt for porosity, electrical resistivity, and shear wave velocity data and divides the sediment into four different soil layers. In particular, there may exist a transitional zone from loose silt to low plastic clay (i.e., depth z = 4–10 m), where the silt tends to be contractive when subjected to cyclic events and plays a critical role in the determination of time to pore pressure dissipation, so that this layer may be sensitive to liquefaction. The factor of safety is calculated based on the field test results to verify the liquefaction potential of fine-dominant sediments where clays prevail. The data interpretation approach and physical model framework proposed in this study can be applied to the evaluation of liquefaction susceptibility for fine-dominant soil deposits.