Study On Cyclic Capacity Of Bucket Foundation On Soft Clay

Being a new offshore platform foundation, bucket foundation has a widely application prospect in developing paralic marginal oil field. However, a lot of soft clay distribute in paralic shallow shoal, there are few research works of evaluating cyclic capacity of bucket foundation on soft clay to reference until now. So the study on cyclic capacity of bucket foundation for soft clay stara is necessary, it will relate to the using and popularizing of bucket foundation in soft clay. In this dissertation, the following works are carried out.First, the changing laws of cyclic strength, cyclic failure criterion and cyclic accumulate deformation are studied under different testing stress states. It is veritied that saturated soft clay followed Mises failure criterion with static and cyclic loads under unconsolidated undrained condition. And the changing laws of cyclic strength and cyclic accumulate deformation built on certain test stress states have generality and can be used in general stress states. A theory basis has been provided for using these laws to evaluate cyclic capacity of bucket foundation on soft clay.Further, cyclic capacity of single bucket foundation on soft clay has been studied through three-dimensional finite element numerical simulating, considering cyclic strength is a changed strength related to initial static stress of each soil element and the number of cycles to failure. And the range of cyclic loads that single bucket foundation can be subjected has been determined under certain static loads for 1000 number of cycles to failure. Based on the study of single bucket foundation cyclic capacity, the influence of bucket spacing has been analyzed for the symmetry multi-bucket foundation static capacity and cyclic capacity. A method has been presented for determining cyclic capacity of symmetry multi-bucket foundation. That is, for certain number of cycles to failure, cyclic capacity of corresponding single bucket foundation has been firstly determined under static loads, cyclic capacity of per-bucket in multi-bucket foundation can be determined considering the influence of bucket spacing subsequently, then cyclic capacity of symmetry multi-bucket foundation can be determined for certain bucket spacing.