Centrifuge Tests on Rock-Socketed Piles: Effect of Socket Roughness on Shaft Resistance

Preliminary estimations of shaft resistance of rock-socketed piles are usually conducted using empirical formulations that relate to the uniaxial compressive strength (σc) 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.