Analysis Of The Vertical Cyclic Bearing Capacity Of Bucket Foundations In Soft Clays

Bucket foundation is a removable offshore platform foundation. It has been concerned by ocean engineering researchers more and more for its unique advantages. The stability of bucket foundation, especially the bearing capacity under cyclic loads in storm, is very important in design. The model tests were conducted to study the bearing capacities of bucket foundations in soft clays under cyclic loads. Test results were simulated using pseudo static elasto-plastic finite element method (FEM) to verify the feasibility of the method to evaluate vertical cyclic bearing capacity ofbucket foundation in soft clays. The relationship between the soil strength and the bearing capacity of soft clay foundation was studied by comparing model test and calculation results using bearing capacity formulas. Based on plate model test results, soil strength and elastic modulus were backanalyzed by FEM using perfect elasto-plastic model and compared with the test soil parameters. The method to choose the parameters in calculating soft clays bearing capacity by FEM was suggested.The stress variation of the bucket foundation was analyzed under static and cyclic loads. The strength model to describe cyclic characteristics of the soft clay was given based on laboratory cyclic triaxial test results. The method and steps were presented to evaluate the vertical cyclic bearing capacity of bucket foundation by pseudo static elasto-plastic FEM.The vertical cyclic bearing capacity model tests of the loading plate and single bucket foundation in the soft clay were conducted respectively. And tests were simulated by FEM according to the different tests conditions using above method. Results indicated that the method to evaluate vertical cyclic bearing capacity using the pseudo static elasto-plastic FEM was feasible. Based on the computation results curves between vertical cyclic bearing capacity and static loads of single bucket foundation were determined corresponding to 500 and 1000 cycles to fail. We can determine the vertical cyclic loads that the bucket foundation could support under constant static load based on them. With a certain cyclic load, we can confirm the maximum static loads that the foundation would endure. Finally, the vertical cyclic bearing capacity of four combined buckets foundation in soft clays was studied. By changing the distance between buckets, the static and cyclic bearing capacities of four combined buckets foundation were researched. Also the relationship of bearing capacities between single bucket and four combined buckets foundation was studied. Vertical cyclic bearing capacity model tests of four buckets foundation which distance between buckets was one time diameter were simulated by pseudo static elasto-plastic FEM. Reasults further indicated that using the pseudo static elasto-plastic FEM to evaluate vertical cyclic bearing capacity of four combined buckets foundation in soft clays is feasible.