During the uplift process of suction caisson foundation

the soil at the bottom of caisson is in an axial unloading state. But there are few studies on the mechanism of the unloading creep of soft clay. Therefore

the axial unloading triaxial creep test on saturated soft clay was carried out to obtain the variation law of axial strain with time and deformation mechanism of soft clay under different confining pressures. At the same time

the long-term uplift test on suction caisson foundation was carried out to analyze the long-term uplift bearing characteristics of suction caisson foundation. The unloading creep test results show that under the condition of the low deviator stress

the unloading creep deformation of soil can be ignored. The unloading deviator stress is higher

the unloading creep deformation is greater and the nonlinear creep characteristics become more obvious. Therefore

by introducing the creep model and considering the influence of the deviator stress

the stress-dependent creep model is proposed to describe the unloading creep of soft clay. Then

the stress-dependent creep model is extended to a three-dimension constitutive model

and a finite element subroutine is developed to establish a finite element analysis method for analyzing the long-term uplift capacity of suction caisson foundations and validated with the long-term uplift bearing capacity results of caisson model.