The loading behavior of innovative monopile foundations for offshore wind turbine based on centrifuge experiments

Abstract

Wind energy is a promising source of renewable energy and is projected to shift to offshore areas increasingly. Monopile foundation is one of the most commonly used foundations for offshore wind applications with the priority in load bearing capability and initial cost. This study describes an innovative monopile foundation, which institutes a creative strategy over the traditional large diameter monopile foundation to achieve higher axially load bearing capacity. This is achieved by adding a restriction plate inside the pile to intensify the soil plug effect. This design is based on the soil plug mechanism, and the arching effects and plug resistance mobilizations are considered. In this study, an extensive amount of geotechnical centrifuge experiments was conducted to analyze the bearing behaviors of the innovative monopile with restriction plates. The pile with 1-hole restriction plate and the pile with 4-hole restriction plate are considered to discuss effects of the plate shape. Twelve models with different diameters and restriction plate types are investigated. The traditional open-ended and close-ended piles are included for comparisons. The static tests are conducted in saturated silica sand first to determine the ultimate bearing capacity of the innovative pile, after which the cyclic tests are performed. The innovative pile is proved to provide a larger bearing capacity than the pipe pile. An analytical method is proposed to estimate the capacity of the innovative pile. The study aims to develop the design code for innovative piles and provide design reference to large-scale offshore wind turbine projects.