The direct shear tests of the interfaces between the concrete and the cohesive soil as well as the sandy soil were conducted by using a large direct shear apparatus,and the stress,strain and failure strength of the inter- faces were investigated under different normal stresses.The results show that the cohesive soil and concrete inter- face has a strain-softening characteristic during the shear,and the residual stress tends to be a constant,and that the sandy soil and concrete interface has a strain-hardening characteristic during the shear,and the residual stress slowly increases.In order to investigate the shear characteristics of the soil and structure interface,by introducing the damage mechanics theory,a constitutive model of shear damage,which considers the strain-hardening and sof- tening characteristics,is constructed,and a method of determining the model parameters is proposed.The con- structed damage model can reflect the strain-softening and hardening characteristics of the soil and structure inter- face with less model parameters,and it is both convenient and practical.