A new kind of practical soil constitutive model by combining Duncan-Chang inelastic constitutive model with the elastoplastic model adapting Drucker-Prager failure has been derived in order to overcome the classical elastoplastic model’s inability to cover the nonlinear behavior of soil before plastic yielding and unsuitability of normal Duncan-Chang model to the stress state approaching yielding or failure .Finally
the numerical examples of practical problems have shown its feasibility and practicability.