This study simulates the shaft resistance of continuous flight auger (CFA) piles in unsaturated tropical soils using the Mohr–Coulomb (MC) and Hardening Soil (HS) models, calibrated with full-scale tension tests at São Carlos, Brazil. Numerical simulations were performed using two-dimensional finite element modelling, incorporating suction effects at the pile–soil interface through suction-dependent apparent cohesion derived from laboratory and field data. A back-analysis of the loading tests and previous investigations was conducted to reproduce the current in-situ stress conditions. To model the field-observed degradation of suction-induced bonding, interface strength was progressively reduced, particularly in upper pile sections, reproducing the transition from peak to residual shaft resistance. Sensitivity analysis assessed the effects of key interface parameters and suction-dependent cohesion on shaft resistance and load distribution along the pile. Both models captured experimental load–displacement trends, with the MC model fitting pre-failure behaviour and the HS model better representing stiffness degradation. Suction-dependent interface strength mainly controls shaft resistance in upper layers, while constitutive stiffness affects displacements. The proposed modelling framework incorporates suction effects and post-peak interface degradation into conventional finite element analyses, providing a practical approach to simulate pile behaviour and improve predictions for unsaturated tropical soils.
Silva et al. (Tue,) studied this question.