Experimental Study Of The Vertical Cyclic Bearing Capacity Of Bucket Foundations In Soft Clay

As a new offshore platform foundation, the bucket foundation has been more and more extensively used in the ocean engineering. Because the foundations will be subjected to long-term cyclic loads such as that from the wave loading in the marine environment, evaluation of cyclic bearing capacity is an essential part of the design of bucket foundations. This paper presents researches on the vertical cyclic bearing capacity of the bucket foundations in soft clay.Firstly, a model test stratum was prepared using the vacuum preload method in a large tank. Model tests were conducted to study the vertical bearing capacity of single-bucket foundations and four-bucket foundations under vertical static load. Based on test results of single-bucket foundations, the applicability evaluating the vertical bearing capacity of the bucket foundations in soft clays using theory equations were analysed and compared. The feasibility calculating the vertical bearing capacity of the bucket foundation by the FEM is studied, and the problem of rationally choosing the parameters of the FEM method in the calculation is analysed. Meantimes, by the FEM calculations of the vertical bearing capacity of four-bucket foundations with different bucket-spacing, the effect of bucket-spacing on the vertical bearing capacity of four-bucket foundations is studied, and a simple method of evaluating the vertical bearing capacity of the four-bucket foundations in soft clay is proposed.The cyclic unconsolidated and undrained properties of soft clay were studied using cyclic triaxial tests, which include variations of cyclic accumulative strain and the cyclic strength with the static stress, the cyclic stress and the number of cycles. The relationships among them were developed to calculate the cyclic bearing capacity of bucket foundations in soft caly.Finally vertical cyclic bearing capacity tests of single-bucket foundations and four-bucket foundations were conducted and analyzed by the pesudo static finite element method using the cyclic strength relationship. The comparison between test and calculating results showed that it is possible to evaluate the vertical cyclic bearing capacity of the bucket foundations in soft clays using the method.