Cyclic loading history is an important parameter to the further dynamic characteristics of soils. A series of draining cyclic simple shear tests on an undisturbed silty clay are carried out; and the development of volumetric strains with the change of load cycles and shear strain amplitude is found out

as well as the correlation between the accumulated volumetric strain and the further dynamic characteristics. The test results show that the volumetric strains increase with the development of cyclic load cycles and the improvement of cyclic shear strain amplitude

and further more with the accumulation of volumetric strain

the dynamic characteristics of the clay soil are strengthened

which means that the dynamic shear modulus goes up and the damping ratio degrades. The effects of accumulated volumetric strains on dynamic shear modulus and damping ratio are analyzed; and some relevant correlation equations are proposed. With the adoption of two coefficients

respectively the coefficient of modulus strengthening and the coefficient of damping degrading

a constitutive model which can take the effect of cyclic load history into account is constructed based on a normal nonlinear model.