Study On Ontimal Design Of Large-diameter Rock-socketed Monopiles For Offshore Wind Turbines

Abundant offshore wind power resources,stable wind speeds,saving land,and small environmental noise constraints are suitable for large-scale development.It is an important measure to adjust the power structure and reduce dependence on fossil energy.China's offshore wind energy resources are very rich,and the wind energy reserves that can be developed and used are about 750 GW.By 2020,China's planned offshore wind power grid-connected installed capacity will reach more than 5000 MW,accounting for about 6%of the country's total power generation.At present,large-diameter monopiles are used in 75%of offshore wind turbine projects with advantages such as simple structure,convenient fabrication and installation,and clear stress conditions.Infrastructure structure.At home and abroad,the safety design and analysis of large-diameter monopiles in soil seabeds have been extensively studied.However,the research on large-diameter monopiles on rocky seabeds is relatively rare.Its basic engineering characteristics,bearing mechanism,long-term service performance evaluation and other aspects need to be studied in depth and systematically.This article takes the rock-socketed monopiles of an offshore wind power project on the southeast coast of Fujian as an example,and uses laboratory tests,numerical simulations,and other methods to study the design optimization of large-diameter rock-socketed monopiles under complex loads.In this study,first,through the laboratory experiments of rocks,study the physical and mechanical characteristics of rock samples under different weathering conditions,explore the reduction law of rock stiffness with weathering degree,analyze the trend of rock stiffness with strain,and obtain the strength index of rock under different weathering degrees.The research focuses on the residual strength and variation of weathered rocks under brittle failure.Subsequently,a weathering degree reduction model that can reflect the influence of weathering degree on the stiffness of the rock was studied;and an ABAQUS compatible subroutine was established in combination with the common Mohr Coulomb strength criterion for engineering to realize engineering applications.Finally,through numerical calculation and analysis,the influence law of rock-buried depth on the stability of large-diameter rock-single single-pile foundation at sea is studied,and the optimal rock-socketing depth is proposed to reduce the engineering cost.Based on the numerical simulation analysis,the residual strength discount can be considered.The research results provide key technical support for the design of large-diameter single pile foundations on rocky seabeds,and can be adopted for the optimal design of rock-socketed pile.