Rock-socketed piles are foundational elements designed to transmit large concentrated loads to stronger materials located at greater depths. The rock-socket side shear resistance is commonly estimated using empirical criteria as a percentage of the rock or concrete uniaxial compressive strength. However, this approach neglects the influence of other important aspects, such as the roughness of the pile-socket interface. In this work, numerical discrete-element models of rock-socketed piles with different degrees of socket roughness are employed to estimate the influence of the socket roughness on the load-settlement response and on the side shear resistance. The numerical simulation results are compared with predictions obtained using empirical correlations based on load test results and proposed by other authors. Results indicate that the discrete-element method is suitable to reproduce rock-socket pile behavior considering socket roughness; they also suggest that sockets drilled with standard tools in soft to medium rock tend to be relatively smooth unless artificially roughened with special tools and that damage to the interface asperities becomes more relevant after socket settlement of about 1% of the socket diameter, especially for rougher piles.

Rock creep behaviour is crucial in many rock engineering projects. Different approaches have been proposed to model rock creep behaviour; however, many cannot reproduce tertiary creep (i.e., accelerating strain rates leading to rock failure). In this work, the distinct element method (DEM) is employed, in conjunction with the rate process theory (RPT) of M.R. Kuhn and J.K. Mitchell (published in 1992) to simulate rock creep. The DEM numerical sample is built using a mixture of contact models between particles that combines the Flat Joint Contact Model and the Linear Model. Laboratory uniaxial compression creep tests conducted on intact slate samples are used as a benchmark to validate the methodology. Results demonstrate that, when properly calibrated, DEM models combined with the RPT can reproduce all creep stages observed in slate rock samples in the laboratory, including tertiary creep, without using constitutive models that incorporate an explicit dependence of strain rate on time. The DEM results also suggest that creep is associated with damage in the samples during the laboratory tests, due to new microcracks that appear when the load is applied and maintained constant at each loading stage.

Preliminary estimations of shaft resistance of rock-socketed piles are usually conducted using empirical formulations that relate to the uniaxial compressive strength (${\sigma }_c$ ) of the weaker material involved (intact rock or pile). However, there are other factors, such as the degree of socket roughness, that could affect the shaft resistance of rock-socketed piles. In this paper, results from geotechnical centrifuge tests are presented to demonstrate the effect of socket roughness on the pile shaft resistance. Aluminum model piles with different degrees of shaft roughness were fabricated and embedded within an artificial rock mixture composed of sand, cement, bentonite, and water. Pile loading tests were conducted within the centrifuge and axial forces along the model piles were measured using fiber Bragg grating (FBG) sensing technology. Results are used to demonstrate that centrifuge testing provides a suitable experimental method to study and quantify the effect of socket roughness on the shaft shearing mechanism of rock-socketed piles. Finally, the centrifuge test measurements are compared with several formulations published in the literature, suggesting that centrifuge measurements tend to agree with the overall trend, despite the variability of predictions obtained with different formulations.