Abstract: In order to study the mechanical properties between silty clay and concrete interface, a series of interface direct shear tests were performed by using a large direct shear apparatus. The interface properties were obtained under different normal stresses (5 kPa, 20 kPa, 50 kPa, 100 kPa and 150 kPa) as well as different moisture contents (12%, 14% and 16%). The following conclusions can be obtained: 1) under the same moisture content, the shear strength at the pilesoil interface increases with the increase of normal stress; 2) under the same normal stress; both the shear strength and the initial tangent shear modulus decreases with the increase of the moisture content; 3) The MohrCoulomb relationship can be used to describe the interface behavior between the silty clay and concrete.

Key words: interface properties;direct shear test, stress-strain relationship, stressdisplacement curves