Development of unified p–y curve model for clays using finite element analysis of laterally loaded piles

Abstract

In this study, a unified p–y curve model is developed for clays in undrained conditions using the results of 3D finite element (FE) modeling. The p–y curves are primarily used in the analysis of laterally loaded piles. Formulas for the ultimate lateral bearing capacity factor ( Np), and the reference deflection in the p–y curve ( y50), were obtained using the results of parametric studies and regression analysis. The tangent hyperbolic function was used to model the p–y curve shape. In the FE models, the clay soil material was modeled as elastic-perfectly plastic material using Mohr–Coulomb criteria, and the pile material was modeled as elastic only. The parametric study results show that Np varies nonlinearly with depth. The proposed model for Np is composed of two regions: a nonlinear zone and a linear zone. The model for Np used the undrained shear strength ( su), effective unit weight of soil ( γ′), and pile width ( D) as parameters. Further, the proposed model for y50 was found to be dependent on the soil stiffness ( Es), D, and Np. The dependency of y50 on Np was often overlooked in previous studies. Finally, the proposed model was imported in LPILE program and the results from previous case studies were compared with the proposed model predictions.