Abstract: A new 3D soil-structure interface test apparatus,which was capable of applying monotonic and cyclic loading in three perpendicular directions,was designed and developed to investigate the mechanical characteristics of the interface between coarse grained soil and structure under 3D loading conditions in most practical projects.Monotonic and cyclic tests could be carried out on large section interface sample by this apparatus with high loading capability.Hydraulic servo system was adopted on each loading direction to generate the desired load or displacement paths on the interface.In the normal direction,three boundary conditions including the constant normal stress,the constant volume and the constant normal stiffness could be imposed,while in the two perpendicular tangential directions,numbers of different loading paths,i.e.,cross,circular and elliptical etc.could be imposed.It was shown that this apparatus could be employed to represent the response of the interface under various loading paths.