Characterization of the interface between concrete pile and coral reef calcarenite using constant normal stiffness direct shear test

This research aims to study the bearing capacity of pre-bored rock-socketed concrete pile on coral reef calcarenite. Constant normal stiffness direct shear test is performed on the interface between the pile and the coral reef calcarenite sample. Observations are made towards the friction mechanism of the pile-rock interface and the consequent shear dilation behaviors. It is shown that the shear failure occurs exclusively inside the coral reef calcarenite. This is attributed to the diffusion and agglomeration of cement paste in the highly porous coral reef calcarenite during the construction. The shear strength of the pile-rock interface increases as the applied normal stress increases. The dilation of the shear failure surface after the peak strength decreases as the applied normal stress increases. When the applied normal stress amounts to 4 MPa, shrinkage is observed for the shear failure surface. When the pile-rock interface slides, the residual shear strength of the interface increases as the applied normal stress increases. Meanwhile, the curve of the residual shear strength versus the shear displacement is affected by the shape and the roughness of the shear failure surface and it fluctuates under different levels of normal stress.