Abstract:Cyclic triaxial tests are conducted on saturated sand under drained conditions with cyclic loading and unloading of spherical stress,and constant deviator stress. The systematic test results are analyzed for the deformation variation with cyclic number and the influence of dry density and consolidated stress condition. It is shown as follows:(1) cyclic spherical stress mainly causes volumetric strain,apparent residual,and cyclic volumetric strain,and the later presents compressive(loading) and swelling (unloading) physical states. At the same time,the deviator strain is very small and can be omitted;(2) the relationship between volumetric strain and the logarithm of spherical stress ratio is linear both in compressive and swelling physical states. The linear parameters have relationship with cyclic number,dry density as well as consolidated stress condition;(3) the linear relation in compressive physical state has some ‘memory’ of consolidated stress,which makes the linear relation a turn at a point of spherical stress under isotropic consolidation,and under anisotropic consolidation it disappears;(4) secondary cyclic loading mainly increases the intercept of the linear relation,and its slope scarcely changes in two physical states;(5) using the revealed law and related parameters,the volumetric strain can be calculated by following spherical stress change and the calculation results are preferably consistent with those by experiment.