Abstract: The unified hardening (UH) constitutive model considering time effect is introduced to describe the elastic viscoplastic deformation of saturated clay, and the Hansbo's flow equation is used to describe the non-Darcy flow through the pore in the consolidation process. Thus the Terzaghi one-dimensional consolidation equation for saturated clay is modified considering the gravity stress of soil layers along the depth direction, and the numerical analysis is performed by using the finite volume method. The applicability of UH model is verified by comparison with the oedometer tests. Then the effects of the gravity stress of soil layers, viscosity, Hansbo's flow parameters, soil thickness and external load on the elastic viscoplastic consolidation process are discussed. The numerical results show that the viscous effect of soils causes an increase of excess pore pressure near the impervious boundary of soil layers at the early stage of loading, and this effect is enhanced by both the gravity stress and the Hansbo's flow, while this phenomenon is weakened with the increase of the external load. In addition, the gravity stress of soil layers can delay the overall dissipation rate of the excess pore pressure in the soil layers at the early stage of loading, and accelerate the consolidation rate of soil layers at the middle and late stages of loading. Moreover, the dissipation of the excess pore water pressure in the soil layers is delayed with the increase of the secondary compression index, thickness of soil layers and Hansbo's flow parameters, but the consolidation rate of the soil layers is accelerated by the increase of the external load.