Numerical Modeling of Flexible Piles in Sand

Motivation

The design of offshore structures, such as wind turbines and oil platforms, depends on the lateral resistance of piled foundations. Design guidelines like API RP 2GEO and ISO 19901-4 provide p-y curves to estimate soil resistance, but their formulations are largely empirical. The latest updates have improved predictions for clayey seabeds, but pile behavior in sand largely remains poorly described, leading to uncertainties in offshore foundation design.

To address this, BP is supporting NGI in a research project that will employ advanced numerical modeling to derive more accurate p-y curves for flexible piles in sand subjected to lateral loading. Using Finite Element (FE) simulations in Plaxis 3D, this study aims to refine soil-structure interaction models and enhance engineering design reliability.

Methodology

The research focuses on 3D FE modeling selecting and calibrating appropriate constitutive soil models:

• SANISAND-MS, which incorporate state- and stress-dependent sand behavior, will be evaluated.
• Comparisons will be made with the Hardening Soil model (HS(S)), a widely used but simpler model.

The extracted soil reactions will be used to develop numerically derived p-y curves, which will be compared with current industry formulations. The study will also examine the effects of sand dilatancy, stress levels, and strain softening, ensuring results align with experimental soil test data.

Objectives

The primary goal is to reduce uncertainties in the lateral design of flexible piles in sand. Specific objectives include:

• Developing improved p-y curves based on FE simulations.
• Investigating the impact of stress-dependent soil behavior on lateral pile response.
• Providing calibration guidelines for numerical models based on laboratory and in-situ test data.

These findings will contribute to enhancing industry-standard design methodologies and informing potential updates to API RP 2GEO and ISO 19901-4.

Deliverables

Upon project completion, NGI will provide BP with:

• A comprehensive report detailing methodologies, findings, and conclusions.
• Plaxis 3D models, including input files for further use.
• Guidelines for calibrating advanced numerical models for lateral pile analyses.

The most relevant scientific aspects of the work are expected to be disseminated through an NGI-led journal publications.