Lateral Bearing Behavior Of Large-Diameter Monopile Foundation Of Offshore Wind Turbine By Considering The Effect Of Wave And Flow

In recent years,the construction of offshore w ind power in China has developed rapidly.The large-diameter monopile foundation is widely used in offshore engineering structures because of its simple structural f orm,high bearing capacity,and easy construction.In addition to the vertical load ca used by the superstructure and its self-weight,the monopile in a complex marine environment is also subjected to lateral loads caused by wind,waves,and currents,etc.On the one hand,it is in a complex stress state;on the other hand,the disturbance and scour by wave and currents will affect the bearing behaviour of the foundations.But the consideration of these factors in the current design method of piles still has relatively large limitations.To this end,based on summarizing the existing research results,the theoretical analysis,indoor flume model test and numerical simulation and other research methods were used to study the lateral bearing characteristics of the large-diameter monopile of the wind turbine in the marine environment,main tasks as follows:First,analyze the wave and currents loads on the offshore wind turbine structure and monopile foundation,the value and actual distribution of the wave and currents loads(including wind load)received by each structural part were calculated.The load-bearing deformation law of large-diameter monopile under wave and currents loads was analyzed.Based on the analysis of soil stress history,the influence mechanism of the soil around the pile by wave and currents erosion is also discussed.Secondly,through independent design and development of indoor test flume model,a series of model pile loading tests were carried out in sand,the bearing characteristics and failure morphology of the large-diameter monopile foundation under different water state were studied.The influence law of the vertical load on the lateral displacement and bending moment of the pile shaft were studied.After the second treatment,the p–y curves of the model pile were obtained,which was compared with the API standards.Through scatter data fitting,the dimensionless envelope of the bearing capacity of the pile under combined load was obtained,and the corresponding simplified calculation formula is given.It can be used for pile design when consider the effects of fluid is needed in practice engineering.Finally,based on the coupling of the ABAQUS standard module and the AQUA module,a three-dimensional numerical analysis model of large-diameter monopile complex loads capable of considering the act ual distribution of wave and currents load and its scouring effect was established.Through model degradation,the results of the model tests in this paper and the existing research results have been compared to verify the accuracy of the model.The parameters analysis was carried out on the pile-soil parameters,the key characteristic parameters of wave and current s,and the pile shaft size,sand strength index,water depth,wave height,period and scouring degree and wind load were applied to the lateral bearing deformation of the wind turbine structure and pile foundation.The law of influence can provide a certain reference for the design and research of l arge-diameter monopile foundation in offshore wind power engineering.