Advanced Soil Constitutive Models for Predicting Soil-Pile-Superstructure Interaction: Evaluating Liquefiable Soil Behavior Under Monotonic, Cyclic, and Seismic Loading

The predictive capability of advanced soil constitutive models under undrained cyclic loading conditions is critical to their practical application, for example, in the field of soil-structure interaction. The hypoplastic framework is one possibility for predicting cyclic responses; however, most hypoplastic models have limitations due to their inability to predict observed trends in strain evolution and excess pore water pressure buildup, which can lead to liquefaction. In this paper we use an improved version of hypoplasticity for undrained monotonic loading (Liao et al., 2024) and combine it with the intergranular strain concept. The new combination with the small-strain extension improves some limitations of the hypoplastic reference model (von Wolffersdorff, 1996) with intergranular strain for undrained cyclic loading. The results of the hypoplastic models are compared to the SANISAND model under different loading scenarios. The validation of the models was done by single-element simulations of experimental monotonic and cyclic triaxial tests. In addition, a 3D finite element model of a soil-pile-superstructure interaction was implemented in ABAQUS and compared with centrifuge test results (Wilson, 1998). SANISAND is effective in predicting the superstructure response; however, it overestimates pore water pressure accumulation. The modified hypoplastic model improves the simulated responses of the soil-pile-superstructure system in terms of pore water pressure and acceleration, compared to the hypoplastic reference model and SANISAND. Our study shows that reliable monotonic models are essential, as it is the basis for reliable cyclic predictions.