Tangent elastic modulus of Duncan-Chang model for different stress paths

In practical applications,the soil might be subjected to different stress paths,such as axial unloading lateral loading and lateral unloading.But the well-known Duncan-Chang model was derived only under the axial loading condition.Thus the scope of its application was restricted.It was attempted to further develop the Duncan-Chang model and to derive a formula of tangent elastic modulus under different stress paths.The new formula was verified for various problems which could not be well handled by the traditional Duncan-Chang model.