Development of an Advanced Nonlinear Finite Element Model for Predicting the Structural Response of Pile-Soil Systems in Soft Clays Under Lateral Loading in the Coastal Niger Delta

The lateral response of pile foundations in the soft clay-dominated geotechnical profiles of the coastal Niger Delta in the South South geopolitical zone determines the structural serviceability and ultimate stability of offshore platforms, quay walls, industrial buildings on reclaimed land, and pipeline bridge crossings that are critical to Nigeria's petroleum and maritime infrastructure. Existing p-y curve models for soft clay lateral pile behaviour were developed primarily from field test data in Gulf of Mexico and North Sea environments, and their applicability to the high-plasticity, high-water-content, and structurally sensitive clays of the Niger Delta has not been validated. This study develops an advanced nonlinear finite element model for predicting the structural response of pile-soil systems in Niger Delta soft clays under lateral loading, incorporating rate-dependent material behaviour, large deformation kinematics using Updated Lagrangian formulation, and an anisotropic critical state constitutive model calibrated against an extensive geotechnical laboratory database from 18 offshore and onshore site investigation campaigns in Bayelsa, Delta, and Rivers States. Model validation was conducted against twelve lateral pile load tests, including four previously unpublished tests conducted as part of this study at sites in Warri and Port Harcourt. Results demonstrate that the advanced finite element model predicts lateral pile head load-deflection response within 12 percent of measured values, compared to 34 percent mean error for the API-recommended Matlock soft clay p-y model on the same dataset. The model correctly captures the progressive strength degradation with increasing cyclic loading amplitude that is characteristic of the metastable Niger Delta clays. The study delivers a validated finite element tool and a recalibrated p-y model for Niger Delta soft clay conditions as original contributions to the field. Keywords: pile-soil interaction, lateral loading, soft clay, Niger Delta, nonlinear finite element.