Analysis of p-y Curve of Drilled Shafts Socketed into Basalt at Jeju Island

The results obtained from a field lateral loading test and the existing p-y curve models were compared to develop a p-y curve model applicable to the basalt at Jeju Island. The results of the comparison demonstrated underestimated values for the initial tangent modulus and the ultimate subgrade reaction from the p-y curve models presented by Carter and Kulhawy (1992) and overestimated values from the p-y curve model suggested by Yang and Liang (2006). Therefore, in this paper, the initial tangent to a p-y curve suggested by Carter (1984) was modified according to the behavior of the basalt at Jeju Island.

Introduction

Recently, the exploitation of offshore wind turbines worldwide has been gradually increasing on the basis of the prospects for a new infrastructure for the energy industry that is currently unavailable for onshore wind turbines owing to issues associated with noise, the landscape, and the deficiency of necessary sites.

Thus, active research on source technologies to establish offshore wind turbine systems and optimal large complexes is currently in progress in Korea. Among the sites of large complexes for offshore wind turbine systems, offshore Jeju Island was determined to be one of the optimal places for an offshore wind turbine system due to its favorable windy conditions. Therefore, efforts to develop a marine wind power generation system and associated planning activities are concentrated there.

The representative types of pile foundations required for offshore wind turbines are the monopole, jacket, and tripod, from which an optimal type of pile foundation is determined by the consideration of various factors such as the type and characteristics of the seabed, the depth of the water, the tidal current, the waves and winds, and the economy.

The pile foundation is a substructure designed to support vertical and lateral loads for places where it is difficult to install direct foundations to support upper-structure loads due to soft ground or places with high-water levels, and it is typically designed to resist axial loads. However, offshore wind turbines are frequently subjected to large lateral loads induced by the wind load, the current load, and wave loads. Thus, pile foundations applied to offshore wind turbines should be designed to resist lateral loads as well as axial loads.