Towards concrete-rock interface shear containing similar triangular asperities

The properties of socket wall significantly affect the loading capacity of a rock socketed pile, and the shear mobilization relies heavily on the roughness of the socket surface and the boundary condition in reality. In this study, laboratory tests have been conducted to investigate the performance of concrete-rock interface shear under constant normal stiffness (CNS) condition and, in particular, an alternative profile to characterize the interface roughness is assembled as series of similar triangular asperities. The profiles of rock samples differing in the dimension of asperities have been divided into five categories (including one kind of regular triangular asperities for comparison). Direct shear tests on the samples are carried out under CNS conditions, with different initial normal loads and normal stiffnesses. The observations indicate that the shear behavior of concrete-rock interface is highly dependent on the uniformity of asperity geometry; compared with the roughness of similar triangular asperities, the one of regular asperities behaves more brittleness and shows a higher peak strength as well as a lower residual strength. In addition to the general tendency, it is found that the local lift-off of some asperities is pronounced relied heavily on their heights, and the redistribution of local stresses can further affect the global shear behavior. The size-dependent sequence of asperity failure can be also observed, confirming the earlier theoretical anticipation reported by the authors. Careful observations during this testing made it possible to develop a micromechanics-based model published elsewhere, and the comparison between them are presented.

Automated summary

The study shows that the shear behavior of the concrete-rock interface is highly dependent on the uniformity of asperity geometry, with regular asperities exhibiting more brittleness. The local lift-off of some asperities is pronounced, depending on their heights, and the redistribution of local stresses can affect the global shear behavior.