Static Stiffness Analysis of an Embedded Bucket Foundation Using Finite-Element Modeling

Abstract

Response of a rigid tube embedded in a homogeneous elastic-half space medium is the most fundamental yet important practice for evaluating the behavior of offshore wind turbine (OWT) foundations. A single degree of freedom (SDOF) spring-mass-dashpot system is deployed to characterize the interaction of a shallow foundation with underlying elastic-half space. The soil structure interaction (SSI) method analyzes a shallow foundation as a rigid body and the surrounding soil as a continuum. It enables modeling of the structure and soil as a single interactive system. Finite-element method (FEM) is a technique based on SSI which allows accurate and detailed evaluation of the soil-foundation system. The first step towards the SSI approach is to determine the static stiffness of the foundation. Our research aims to utilize FEM tools to compute the vertical static stiffness of a rigid tubular foundation and conduct parametric study based on the embedment depth, wall thickness of foundation, and Poisson’s ratio of soil. Foundation designs can be optimized and improved in terms of safety and stability by using modern techniques of FEM to determine foundation stiffness using footing parameters like the embedment depth, wall thickness and soil parameters like Poisson’s ratio. Gazetas et al. (1985) formulated empirical solutions of static stiffness of rigid foundation by incorporating trench and side wall factors. Aubeny (2023) provides a wall thickness dependent factor for evaluating the static stiffness of a rigid circular footing. Our objective is to compare the existing literature solutions using the principle of superposition with numerically computed values and propose modified equations of vertical static stiffness as a function of the foundation and soil parameters.