Abstract: The mechanical behaviors of pile foundation are restricted by the shear behavior of pile-soil interface which is of importance for the study of pile-soil interaction mechanism. In this research, shear tests on marine clay-steel interface and marine clay-concrete interface were conducted via an improved direct shear apparatus to investigate the relationship between shear stress and shear displacement of interface with varied water content and consolidation time. Results indicate that relationship between shear stress and shear displacement of interface displayed good elastic-plasticity which can be expressed by hyperbolic model. The peak shear stress and displacement of interface increased with the climbing of normal stress, the declining of water content and the extension of consolidation time. The increment of peak shear stress concentrated within 14 days after consolidation. Moreover, the friction angle and cohesive force of interface decreased with the climbing of water content. Consolidation time had little influence on the friction angle of interface which concentrated in the range from 20 degrees to 23 degrees. The cohesive force of interface increased with the increasing of consolidation time, and such increment concentrated within 14 days after the initiation of consolidation. The research findings provide reference for estimating the resistance during the pile driving stage and for numerical simulation of marine pile foundation engineering.

Key words: marine clay, shear behavior of interface, water content, consolidation time, improved direct shear test