Seepage Flow Analysis and Performance-Based Assessment of Pile Groups Under Eccentric Loading and Scour Conditions

This study presents an integrated approach for assessing the response of pile foundations in riverbeds subjected to seepage flows and eccentric loading under scour conditions. The main objectives are twofold: first, to investigate the influence of seepage-induced pore pressure variations on the effective stress state of the foundation soil; and second, to develop a simplified performancebased method for evaluating the behavior of the foundation under both localized and generalized scour. Three-dimensional Computational Fluid Dynamics (CFD) simulations were carried out using Ansys Fluent to determine hydraulic pressure distributions along the riverbed. These pressures were then applied as boundary conditions in a three-dimensional geotechnical model developed in FLAC3D to assess pore pressure distribution and its effects on soil stress state. The results indicate that seepage flows do not significantly alter the global bearing capacity, but they locally affect the stress conditions and may contribute to the initiation and progression of scour. The performance-based analysis of the eccentrically loaded foundation was conducted by constructing two-dimensional interaction domains in the Q-Mx and Q-My planes using a simplified methodology capable of accounting for both Serviceability Limit State (SLS) and Ultimate Limit State (ULS) conditions. In this framework, pile group effects are modeled through interaction coefficients derived from a Boundary Element Method (BEM) solution. The contribution of the pile cap is neglected and the connecting structure is modeled as infinitely rigid. The approach is applied to a well-documented case study.