Abstract

This paper presents preliminary results of an extensive programme of three-dimensional finite element analyses investigating the behavior of laterally loaded piles embedded in soft and stiff clay soils. This paper is primarily focused on larger piles with diameters varying between 4m and 10m which are becoming more common in offshore Oil & Gas and Wind Industries. The model was compared and validated against well-established results from literature. Lateral soil reaction curves obtained from three-dimensional finite element models were compared with the ones obtained from conventional p-y approach recommended in the standard codes. Some recommendations were obtained from the results of this sensitivity analysis which can be used in the design of this kind of piles which are used in different sectors e.g. monopiles for Wind Turbine Generators, piles to support jackets and suction caisson foundations employed in the offshore energy sector.

Introduction

Piles have been commonly used in the offshore industry to provide support for fixed and floating structures against lateral loads and overturning moments resulting from operation loads, e.g. expansion or contraction of pipelines and jumpers, or environmental loads such as wind, wave and current loads. While slender piles have been routinely employed in the offshore energy industry for many years, larger piles with diameters varying between 4m and 10m are becoming more common for different purposes such as typical foundation for offshore/subsea structures or mooring anchors for floating facilities. This kind of piles are also being used/considered for the current and future offshore wind projects.

Conventional design approaches are generally based on lateral soil reaction curves, known as p-y curves, provided by standard codes such as DNVGL (2016) and API (2010). However, there have been concerns that these design methods might be inappropriate for large diameter piles as these were developed for small diameter and more flexible piles as shown by Reese and Matlock (1956), Matlock (1970), Reese et al. (1974), Cox et al. (1974). Generally, conventional design approaches are first used to calculate the required pile geometry to resist lateral loads applied to the pile. Then, these soil reaction curves will be passed to structural engineers who would use these soil reactions as an input to the structural models. It has also been observed that while the finite element method has been used by a number of designers to derive pile geometries, soil reaction curves based on recommendations in standard codes such as API and DNV are provided to the structural engineers, as the process of extraction of soil reaction curves from commercial finite element packages is not generally straightforward.

This content is only available via PDF.
You can access this article if you purchase or spend a download.