Local Scour around a Monopile Foundation for Offshore Wind Turbines and Scour Effects on Structural Responses

Abstract

Monopile is the most commonly used foundation type for offshore wind turbines. The local scour at a monopile foundation generated by the incoming shear flow has significant influence on both quasi-static lateral responses and dynamic responses of the monopile. This chapter focuses particularly on characterizing the local scour in both spatial and temporal scales and revealing the scour mechanisms associated with the flow field around a monopile. The predicting methods for the equilibrium scour depth and the time scale of scour are detailed under various representative flow conditions in the marine environment. The scale effect while extrapolating the results of model tests to prototype conditions is highlighted. The local scour imposes significant influence not only on the deformation and stiffness of the monopile foundation, but also on the natural frequency and fatigue life of the structure system. Monopiles with diameters up to 10 m have become a feasible option as the industry is currently advancing into deeper waters. More meticulous considerations for monopile design associated with the scour depth prediction and evaluation of scour effects are still in need to efficiently minimize the cost while remaining safety simultaneously.

Winds of Change: Urgent Challenges and Emerging Opportunities in Submerged Prehistory, a Perspective from the North Sea

“…The implications vary with sediment composition; for example, areas underlain by marine clay show limited scour, while those with sandy sediments may experience scour depths up to 1.38 times the monopile diameter [121]. Monopiles with diameters up to 10 m are now feasible as the industry advances into deeper waters [122].…”

Long-Term Response of Sand Subjected to Repetitive Simple Shear Loading: Shakedown, Ratcheting, and Terminal Void Ratio

“…Low-stress regimes have been explored in the context of traffic loads on granular bases (pavements and railroads) and seismic loads. In this study, we placed emphasis on higher stress regimes such as those created beneath tall buildings and adjacent to monopole foundations for wind turbines (Qi and Gao 2019;Ahmed and Hawlader 2016). All specimens experienced the same loading history (Fig.…”

Lateral Bearing Capacity of a Hybrid Monopile: Combined Effects of Wing Configuration and Local Scour

“…The bigger turbine size and deeper water depth bring out larger loads, which require more reliable and powerful foundations to resist them. Several new hybrid monopile foundations are proposed to support large-capacity wind turbines operating in deeper waters at a reasonable cost [6].…”