Design of Foundations for Offshore Wind Turbines

4 Geotechnical Site Investigation and Soil Behaviour under Cyclic Loading

Learning Objectives

This chapter discusses the site investigation and the soil testing required for obtaining the parameters for carrying out the foundation design. The chapter will also discuss the advanced soil testing apparatus that may be used to obtain the design parameters. There are plenty of text books on site investigation and soil testing and therefore those topics are not discussed in detail in this chapter. However, references are provided for those topics for guided learning.

4.1 Introduction

As discussed in Chapter 2, foundation design requires not only ground profile but also information on wind, waves, and site‐specific geohazards, including natural hazards (e.g. seismic). However, this chapter is devoted to ground investigation, i.e. data and ground/soil parameters necessary for foundation‐related design. Site Investigations related to ground are necessary for the following:

1. Foundation design for the turbine support structure and offshore substation structure. See Chapter 1 for a typical wind farm layout.
2. Cable route. Chapter 1 shows the layout of a wind farm, and there are two types of cables (inter‐array and export cables) to transmit the electricity generated to the onshore grid. Investigations are necessary along the cable route for design purposes. The major considerations are: scour prediction, cable protection, and turbidity changes in the water. Turbidity changes ...