【英文摘要】Following conclusions were clarified by cyclic soil tests with different stress states. The UU cyclic strength of soft clays obeys Mises failure criterion. Undrained static and cyclic strengths of k0 consolidation clays can be approximately described by Mohr-Coulomb failure criterion. The degradation of the undrained cyclic strength is less than 3% if the cyclic stress period increased from 10s to 100s and the number of cycles to failure is less than 1000 for k0 consolidation clays. The effect of cyclic period on the cyclic strength can be neglected if the number of cycles to failure is larger than 1000. Three typical failure modes of suction anchors are revealed by a large number of bearing capacity model tests of anchors under static and cyclic loads, which are modes of vertical pullout from strata, lateral squeezing strata and inclined upward squeezing strata. Failure mechanisms associated three failure modes are analyzed by FEM calculations. Model tests also show that the failure mode of anchors may be changed under cyclic loading and the cyclic bearing capacity will obviously decrease. The largest degradation is about 75% if the number of cycles to failure is less than 1000. Tests reveal that the degradation of cyclic bearing capacity is less than 8% if the period of cyclic load increases from 10s to 100s and the number of cycles to failure is less than 1000 and the effect of the period on the bearing capacity can be neglected if the number of cycles to failure is large than 1000. Three kinds of method evaluating the cyclic bearing capacity of suction anchors in soft caly are developed in the research, which are the elastoplastic 3D finite element method, the limiting equilibrium analysis method and the upper bound plasticity analysis method. Their reasonability are verified by model tests. The multifunctional servo-controlled electric loading device is successfully developed and the Chinese invent patent has been applied for it.