Analyses on Deformation Procedure of Suction Anchor Foundations Subjected to Static and Cyclic Loads

摘要

The paper presents a pseudo-dynamic constitutive relationshipdescribing undrained stress-strain responses of soft clays subjected tocyclic loads based on the equivalent visco-elastic theory and the creeptheory. The relationship includes three basic parameters: the equivalentcyclic shear modulus, the equivalent damping ratio and the cyclicaccumulative strain increment. The nonlinearity of cyclic stress-strainresponses of soft clays is described using variations of the cyclic shearmodulus and the damping ratio with the octahedral shear strain. Thecyclic accumulative strain is described using the equivalent creep. Thecyclic accumulative strain increment is determined using the Misescreep potential function and the associated flowing rule. They can bedetermined by unconsolidated and undrained cyclic triaxial tests of softclays. A pseudo dynamic visco-elastoplastic finite element method toanalyze the deformation instability process of suction anchorfoundations subjected to static and cyclic loads in soft clays wasdeveloped using the constitutive relationship. For the method, a cyclicloading time history is divided into a series of incremental cyclicloading processes which includes one load cycle at least. Detailedcyclic stress-strain responses of soil elements at any time are nottracked but they are determined by the equivalent visco-elasticcalculations for each incremental loading process. The cyclicaccumulative strain increment of soil elements is determined based onthe static stress, the cyclic stress of soil elements and the incrementalnumber of load cycles. The cyclic accumulative deformation of suctionanchor foundations is calculated using the initial strain method. Modeltest results of suction anchors subjected to inclined static and cyclicloads at the optimal load point are predicted using the method.Comparisons of predicted and model test results show that predictedthe deformation instability process of suction anchor foundations arebasically in agreement with model test results.