The results of triaxial creep experiments for unloading state show that the frozen soil has an obvious dilatancy

and its volume strain should not be neglected. To fully reflect creep deformation laws of frozen soil under unloading state

a rheological constitutive dynamic model of frozen soil submitting to ellipse-DP two-yield-surface is put forward by using Nishihara model as the basic element. And the model is embedded in ADINA finite element program on the base of secondary developing technique for finite element program. The results of numerical simulation for triaxial creep experiments show that the constitutive dynamic model of ellipse-DP two-yield-surface can reflect some deformation properties of dilatancy and volume strain of frozen soil very well; and it can coincide with the experimental data

which can provide references for frozen projects calculation.