Abstract: Direct shear tests are carried out to investigate the influence of the interface on the mechanical behaviors of bi-material and the bi-body.A special specimen,casted with both mortar and concrete and formed irregular asperities in the interface between bi-material is employed to simulate the interaction of structural body and geo-body.According to the direct shear tests,the failure pattern and stress-displacement curves of bi-material specimens and bi-body specimens are analyzed.The main results are as follows:the cohesion effect and normal stress have a key influence on the mechanical behaviors of the interface;and under the middle-and low-grade normal stresses,the shape factor λ has an important influence on the shear mechanical properties of the interface of bi-body.However,under the high normal stress,the shear mechanical properties of the interface are determined by the strength of attenuating medium.Because of the difference of the failure pattern force form,under the middle-and low-grade normal stresses,the peak shear strength of the bi-material specimens is larger than that of the bi-body specimens.However,under the high normal stress,the result is opposite.