Abstract

Offshore wind turbines (OWT) subjected to long-term complex marine loads are prone to foundation damages, affecting their regular operation. However, the failure mode of the large-diameter monopile foundation under complex marine loads is not well understood. Hence, failure modes of monopile foundation for OWT in soft-soil seabed under unidirectional and multidirectional loads are investigated. Firstly, the mechanical characteristics of soft soil are tested indoors. Subsequently, the monopile foundation failure modes under unidirectional loads are examined, which indicates capacity failures of monopile foundation are progressive, and two distinct soil failure mechanisms are identified. Then, the failure modes and failure envelopes under multidirectional loads (horizontal load, vertical load, and bending moment）are explored. Results show that the failure envelopes in H–V and M–V load space are oval-shaped, and failure modes in H–V and M–V load space are characterized by wedge failure. More critically, the service performance of the monopile foundation in soft soil in a full lifecycle can be estimated by the location of the actual loads in the failure envelope. Finally, the effect of pile diameter on the bearing capacity of the monopile foundation for OWT under unidirectional and multidirectional loads is discussed.

摘要

海上风电机组（OWT）长期承受复杂的海洋载荷，容易发生基础损坏，影响其正常运行。然而，大直径单桩基础在复杂海洋荷载作用下的破坏模式尚不清楚。因此，研究了单向和多向荷载作用下软土海床OWT单桩基础的破坏模式。首先，在室内测试软土的力学特性。随后，研究了单向荷载作用下的单桩基础破坏模式，表明单桩基础的承载力破坏是渐进的，并确定了两种不同的土体破坏机制。然后，研究了多向载荷（水平载荷、竖向载荷和弯矩）下的失效模式和失效包络。H - V和M - V载荷空间呈椭圆形，H - V和M - V载荷空间的破坏模式以楔形破坏为特征。更关键的是，软土中单桩基础在整个生命周期内的使用性能可以通过失效包络线中实际载荷的位置来估计。最后，讨论了单向和多向荷载作用下桩径对单桩基础承载力的影响。