The conventional triaxial tests for cement-soil show stronger soften characteristics of cement-soil under low confining pressure. The soften character is weaken as confining pressure decrease. For adopting Duncan-Chang hyperbola model to obtain parameters of cement-soil, the model cannot include the stress-strain soften characteristics of cement-soil, and must be discussed. The paper studies on parameters of Duncan-Chang model using generalized Hooke law and nonlinear elastic theory. The researches show the parameters of k and n are unrelated to soften characteristics of cement-soil; the relation of Rf and σ3 is given by the soften characteristics, Rf influence the soften process directly. The calculation method could be used in E-u model, and has good practical value.
