Centrifuge modelling of jacket foundation subjected to cyclic lateral loading in soft clay

The centrifugal model tests are carried out on a jacket foundation subjected to cyclic lateral loading in saturated soft clay to investigate the force and deformation characteristics of the jacket foundation under cyclic lateral loading from wind and wave. The forces and displacements of the jacked top, displacements of piles head and bending moments of the pile shaft are measured. Based on the measured bending moments, the lateral displacements and the soil reaction forces around piles are calculated. The test results show that under the cyclic lateral loading, the load-displacement curve of the jacket foundation head exhibits an obvious nonlinearity. The lateral deformation of the trailing-row piles is about 80% of that of the leading-row ones, while both of their deformations are less than those of the jacket top, which leads to a certain angle of inclination on the jacket foundation. The peak bending moment of piles appear around 6D below the soil surface. The hyperbolic tangent p-y curves are used to fit the test results and they are compared with the API code. It is found that the initial stiffness and ultimate shallow layer soil reaction are smaller, and the calculated results are too conservative according to the API code. Furthermore, it is revealed that the cyclic degradation of the soil reaction under soil surface within 5 times the diameter in depth should be taken into account, and the degradation of the leading-row piles is obviously larger compared with that of the trailing-row ones, which should be separately considered in engineering design.