Load transfer in drilled piles for concrete-rock interface with similar triangular asperities

For drilled piles in rock stratum, predictions of axial load-deformation response offer guidance for the preliminary design. In this development, the profiles of socket wall would be idealized as similar triangular asperities, and the expansion of the shaft is laterally confined across the socket wall under constant normal stiffness conditions (CNS). The side shear resistance contributes from the overriding (dilation) and degradation (shearing) of asperities, and the degradation of asperities develops asynchronously. In particular, a correlation is derived between asperity geometry properties and the global strength by including a simplified degradation criterion of the asperity. The proposed model can be considered as a generalization of Patton's model, extending the case of regular triangular asperities to the similar ones. On this basis, the predicted shear mobilization relative to displacement can then be employed to update the load transfer function. Semi-analytical solutions to this problem have been conducted by a finite-difference scheme. Based on the validation of a case study, the proposed prediction exhibits general accuracy with reference to the field observations. To investigate the effect of asperity inclination on the ultimate and residual strengths, a parametric study has also been conducted afterwards. Comparing with an existing method, the prediction from the proposed model captures a ductile response and depicts a notable nonlinear behavior.