Study On Hydraulic Pressure Lifting Process Of Bucket Foundation In Clay

With the development of offshore wind power in recent decades,the bucket foundation has been widely used in marine engineering due to its unique advantages.The subsequent problem is the removal and recycling of the bucket foundation after the expiration of the service period.The demolition and recycling of structures is not only a very dangerous project,but also restricted by environmental,economic and technological factors,Therefore,the research on the recycling process is very meaningful.Currently,there is little research on the recycling process of the bucket foundation.In this paper,FEM and Small-scaled model test are conducted to reveals the development law of the lifting of the bucket foundation and the law of overcoming the lateral friction of the bucket,based on the analysis of static pull-up failure mode,a calculation method suitable for hydraulic jacking resistance is proposed,based on numerical calculations,the factors affecting the hydraulic pressure lifting resistance are analyzed.The main contents and results are as follows:(1)Through the indoor model test of the bucket foundation in the clay foundation.The effect of the length-diameter ratio and the rest time after the sinking on the lifting tension of the bucket foundation was studied,which reveals the rules of the lateral friction resistance and the axial force of model bucket.The change of excess pore water pressure in the soil inside and outside the bucket foundation with time during the lifting of the cylinder base was monitored over time.(2)Based on the ABAQUS finite element software,using the Surface-based cohesive behavior,the change rule of the hydraulic pressure lifting resistance of the tubular foundation with displacement was calculated.By comparing with the model test jacking resistance,the rationality of the numerical method is verified,calculated and analyzed the prototype bucket foundation.the influencing factors of the pull-out resistance and the proportion of the resistance of each part on the cylindrical basis were analyzed.Based on ABAQUS steady-state seepage analysis,the reason for seepage failure during jacking is explained.(3)Discuss and analyze the three failure modes of the cylindrical foundation pulled up statically,based on the existing static uplift calculation method,a calculation method suitable for the hydraulic lift resistance of the bucket foundation is proposed,the applicability of the method is verified by comparison with the measured results of model tests.(4)The effect of different factors on the jacking force of the bucket foundation is studied by numerical analysis,and based on the distribution law of side friction of the cylinder wall,etc.The reasons for different factors affecting the jacking force of the bucket foundation are quantitatively analyzed from the mechanism.