Abstract:The viscoelastic model,which consists of spring and dashpot,has been widely used in geotechnical engineering as it has explicit physical and mechanical meaning. Generally,the model and its parameters obtained from creep test in one-dimension,are applied to the model in three-dimensional geotechnical engineering based on a few hypotheses,such as constant Poisson¢s ratio,constant volumetric modulus and so on. While parameters of the viscoelastic model are differently used in creep test and in geotechnical engineering,and their conversion relations are not definitely presented in the predecessor¢s studies. Especially,the fact that viscous parameters should be changed accordingly is often ignored. In this paper,the creep equations in one-dimension with the above hypotheses are indirectly obtained from the equations in three-dimensions. The conclusion that the creep equations are different with different hypotheses in one-dimension is drawn. Then,the method to determinate parameters of the viscoelastic model is suggested. As an example,the generalized Kelvin creep equations with the hypotheses are solved with the proposed methods and contrasted with the common creep equation without hypothesis. The conversion relations of model parameters under different hypotheses are presented and validated by a geotechnical engineering instance.