An enhanced micromechanical rock-pile interface model with application to rock-socketed pile modeling

The increasing use of rock-socketed piles highlights the importance of developing a suitable design method for their bearing capacity. This study quantifies the shear behavior of the rock-pile interface, which generally dominates the bearing capacity of rock-socketed piles under service load. A micromechanics-based rock-pile interface model with idealized nonuniform profile is proposed with two enhancements: (1) the slip line method together with nonlinear Hoek-Brown failure criteria is integrated to identify the critical shear displacement of rock asperity; and (2) the residual stage of shear behavior is properly considered with the rounding progress of sheared rubbles. The enhanced interface model is first validated by the direct shear test results under constant normal stiffness. Then, the interface model is implemented via user-defined FRIC into the finite element code ABAQUS without the need of explicitly building the rock-pile interface profile. Accordingly, the model is applied to simulate and analyze two field cases involving rock-socketed piles. Comparison between the predictions and field observed results shows this method can well capture the axial load transfer behavior of pile socket into weak rock.