Modification of Bearing Capacity of Rock-Socketed Pile: Considering Concrete–Rock Interface Roughness and Initial Stress of Concrete

The mobilization of side resistance has a significant effect on the load transfer characteristics and the ultimate bearing capacity of rock-socketed pile. A better understanding of the shear mechanism of the concrete–rock interface is of great significance to the load transfer of rock-socketed pile. However, the calculation of the bearing capacity of rock-socketed pile in the current code does not consider the effects of the roughness of the concrete–rock interface and the initial stress of concrete. A series of direct shear tests of concrete–rock samples confirm that the shear strength of the concrete–rock interface increases with interface roughness and concrete initial stress. The numerical results show that roughness and concrete initial stress can significantly affect the friction resistance distribution of pile, especially for hard rock. A modified formula of vertical bearing capacity for rock-socketed pile is presented based on numerical simulation. The results show that the modified formula can better describe the bearing characteristics of rock-socketed pile, and the calculated results are closer to the measured values than the specifications in two real experimental cases.