Two-Dimensional Nonlinear Site Response Analysis of Fines-Dominated Subsoil for Assessment of Liquefaction Potential Using the UBC3D-PLM Model

This study presents a comprehensive site-specific two-dimensional nonlinear ground response analysis of a fines-dominated subsoil profile using the UBC3D-PLM model within the framework of nonlinear finite-element analysis. The UBC3D-PLM model is calibrated using the results of the undrained cyclic response of Bonnie silt from the Verification of Liquefaction Analysis by Centrifuge Studies project. This constitutive model can simulate cyclic behavior and evaluate the excess pore-water pressure ratio (ru) approaching the liquefaction triggering criterion, ru = 1, thereby enabling the model to predict liquefaction potential in fines-dominated soils subjected to seismic loading. The study also examines the influence of nonplastic fines on liquefaction susceptibility using the 1987 Superstition Hills (SH) earthquake at the Wildlife Liquefaction Array (WLA) site as a case study. The response of the UBC3D-PLM model, in terms of surface motion characteristics and alteration of the frequency content of the ground motion at the WLA site, is evaluated and compared with the recorded field data. The fines-dominated sandy layers, confined between two relatively impermeable strata, have liquefied, leading to severe liquefaction-induced sediment ejecta. The computed ejecta potential index for the WLA site, due to the north–south component of the 1987 SH earthquake, is more than 200, which confirms an extreme surface manifestation of sediment ejecta. These results closely match the recorded observations made in and around the WLA site after the postearthquake event.