Abstract：Based on the testing results of interface between soil and structure from direct shear and simple shear test under high stress,research on the differences of interface mechanical properties between two testing situation was done from several aspects such as interface constitutive law,interface shear stiffness,interface friction angle and so on. The results are as follows: the relationship displays nonlinear elastic characteristic between shear stress and tangential displacement of interface in direct shear under high stress,which can be described by the hyperbolic model,but the complete shearing deformation process of interface in simple shear can be characterized as nonlinear elastic-perfect,the essence of hyperbolic model is inconsistent with the testing data from the simple shear; the shear stiffness of interface doesn 't reduce to zero in direct shear test,but interface after shearing strength in simple shear is always in a state of zero shear stiffness; mohr-coulomb strength criterion without cohesive strength is more suitable to express the regressive relationship between shear strength and normal stress; the significance of influential factors for the initial shear stiffness is not the same under two different shear test; theoretical explanation for the difference of interface friction angle is given by use of Taylor 's interface flow rule with the help of Davis relationship,meantime,the results of interfacial shear test under high stress confirm the reasonableness of this explanation.

Keyword：high stress;soil-structure interface;single and direct shear testing;mechanical properties difference;