Research And Application On Capacities Of Multi-bucket And Multi-compartment Bucket Foundations On Soft Clay Under Combined Loading

As the urgent demand of mankind for marine resources and energy,and the rapid expand of offshore oil,gas and power industries,the development and utilization of marine resources will face unprecedented development and challenges.Suction bucket foundations and other new types of structures have been widely used and rapidly developed in trestles,breakwaters,offshore wind turbines and platforms under soft clay and severe marine conditions,and its excellent bearing capacity,economical and environmental advantages,and the advantages of being easy to transport,install and recycle have won broad market prospects.In addition to the long-term effect of vertical load caused by self-weight,suction bucket foundations also frequently suffer from the combined action of horizontal load and moment caused by environmental load.However,the theoretical exploration of their bearing capacity,safety and stability is still lagging behind the engineering practice in China and abroad,while its domestic theoretical exploration and engineering practice is backward compared with other countries,especially multi-bucket and multi-compartment bucket foundations.In this paper,finite element models of tetrapod bucket foundation offshore wind turbines and platforms,tetrapod bucket foundation trestles,box bucket foundation breakwaters and circular-rectangular foundation breakwaters are established.The ultimate bearing capacities under uniaxial loading and failure envelopes under combined loading are calculated.The effects of such factors as foundation spacing,foundation embedment and soil strength heterogeneity on their ultimate bearing capacities and failure envelopes are discussed.The main contents of this article are:(1)Finite element models of tetrapod bucket foundation offshore wind turbines and platforms are established.Their ultimate vertical,horizontal and moment bearing capacities,as well as the VH,VM,HM and VHM failure envelopes are calculated.The effects of foundation spacing,foundation embedment,soil strength heterogeneity and load direction on their ultimate bearing capacities and failure envelopes are discussed.(2)Finite element models of three structures,including tetrapod bucket foundation trestles,box bucket foundation breakwaters and circular-rectangular foundation breakwaters,are established.Their ultimate vertical,horizontal and moment bearing capacities,as well as the VH,VM,HM and VHM failure envelopes are calculated.The effects of foundation bucket spacing,foundation group spacing,foundation embedment and soil strength heterogeneity on their ultimate bearing capacities and failure envelopes are discussed.(3)Taking the Tianjin Port box bucket foundation breakwaters as an example,based on the Einav and Randolph softening and rate effect models of soft clay,its VHM failure envelope under cyclic load is calculated.The effects of foundation embedment and soil strength heterogeneity on its VHM failure envelope under cyclic load are discussed.(4)Formulas for evaluating the ultimate bearing capacities and failure envelopes of tetrapod bucket foundation offshore wind turbines and platforms,tetrapod bucket foundation trestles,box bucket foundation breakwaters and circular-rectangular foundation breakwaters are proposed,to provide theoretical support and design reference for promoting the widely use of these structures in the field of port and marine engineering.