Abstract：On the basis of the theory of BBM model and elastoplastic two-surface model，an elastoplastic two-surface model for unsaturated soils considering the anisotropy under static and cyclic loading is established. A hardening parameter reflecting the anisotropy is introduced in the model. The initial anisotropy is reflected by the initial value of the anisotropy parameter and the evolution of the anisotropy produced by cyclic loading is described by rotation hardening rule. The model contains a bounding surface and a loading surface，which evolve according to the isotropic hardening，kinematic hardening and rotational hardening rules in the stress space. Besides，radial mapping rule and mobile memory center are adopted to reflect the cyclic plastic characteristics of unsaturated soil. The comparison between experimental results and model simulations shows that the proposed model is capable of describing the anisotropy and dynamic mechanical behaviors of unsaturated soils under cyclic loading.
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