Performance-Based Seismic Evaluation of Single Pile and Pile Groups in Layered Soil using PLAXIS 3D

The seismic design of deep foundations requires accurate prediction of structural damage using the Performance-Based Seismic Design (PBSD) framework, which focuses on evaluating Engineering Demand Parameters (EDPs) such as Maximum Bending Moment (M(max)) and Peak Curvature (M(max)). This study conducts a comprehensive numerical investigation into the dynamic response of single piles and various pile group configurations (e.g., 2 x 2, 3 x 3) embedded in layered soil under seismic loading. The methodology utilizes the 3D Finite Element Method (FEM) via PLAXIS 3D to perform Time History Dynamic Analysis (THDA) with non-linear constitutive models, which is essential for accurately simulating complex Soil-Pile-Structure Interaction (SPSI) and the effects of dynamic pore water pressure generation in liquefiable strata. Review of existing literature confirms that while pile groups introduce significant Pile Group Interaction (PGI) leading to amplified internal forces (up to 192% in shear) compared to single piles, they can simultaneously lead to reduced vertical settlement. The foundation's performance is highly sensitive to variations in soil stiffness, damping ratio, and the specific characteristics of the earthquake record (duration, intensity, spectral content). Addressing a critical research gap, this project establishes an integrated parametric framework to simultaneously evaluate the combined influence of these variables across different pile group sizes. The results provide essential quantitative data to inform reliable performance-based design and vulnerability assessment for deep foundations in complex, seismically active geotechnical environments.