复合加载模式下单桩复合筒型基础地基承载力包络线研究

海上风力发电机属于高耸结构物，其地基基础不仅要承受上部结构传递的竖向荷载V、水平荷载H，更要抵抗巨大的弯矩荷载M。单桩复合筒型基础是新型的海上风力发电机基础型式，建立复合加载模式下单桩复合筒型基础地基的破坏包络线，并据此评价其稳定性是地基基础设计的重要手段。在Swipe加载方法和固定位移比加载方法的基础上，通过数值分析研究了不排水饱和软黏土中单桩复合筒型基础在V-H、V-M、H-M和V-H-M加载模式下的地基承载力包络线，开展了室内模型试验，验证了数值分析结果的可靠性。研究表明，V-H和V-M加载模式下地基承载力包络线具有对称性，而H-M加载模式下呈非对称性；V-H-M加载模式下地基承载力包络线的形状受弯矩荷载M的影响显著，表现为随着弯矩荷载的增加，V-H平面内的破坏包络线逐渐缩小。实际工程中，可根据受力状态与破坏包络面的相对关系，评价单桩复合筒型基础的稳定性。

Failure envelopes of single-pile composite bucket foundation of offshore wind turbine under combined loading conditions

The wind turbine is a high-rise structure, which is subjected to both the vertical loading due to structural weight and the horizontal loading and moment due to blade-induced or tower-induced loading. In designing offshore platforms, it is crucial to evaluate the overall stability and the failure mechanisms of the single-pile composite bucket foundation of the wind turbine under combined loading conditions. Based on the Swipe test loading method and the fixed displacement ratio loading method, this paper investigates the failure envelopes of the single-pile composite bucket foundation on the soft soil ground under undrained conditions in the V-H, V-M, H-M and V-H-M spaces by using the finite element method. It is shown that the failure envelopes in V-H and V-M space are symmetrical, while the failure envelope in H-M space is asymmetrical. Moment load affects the shape of failure envelope in V-H-M space, the failure envelopes of V-H space recedes as the moment load increases. By using the relationship between the actual combined loading and the computed failure envelopes, the stability of single-pile composite bucket foundation can be evaluated in engineering practice.