Abstract: An elasto-plasticity damage constitutive model(EPDI model) was developed to unitedly characterize monotonic and cyclic behavior of interface between structure and coarse grained soil.A new model framework was presented and as a result the formulation and parametes determination of the model were set up based on the constitutive rules from test results.The monotonic and cyclic shear tests of the interface under various normal boundary conditions were conducted and also predicted with EPDI model.The predicted results were in good agreement with the test results.Thus,the effectiveness of EPDI model was confirmed to reasonably describe the fundamental behaviors of the interface,including coupling of shear and volumetric strains,evolution of physical state,aeolotropy of response,and influence of normal stress.