Research on shaft resistance of rock-socketed piles based on the cavity expansion theory

The shaft resistance of rock-socketed piles depends not only on the properties of its surrounding rock, but also on the radial force induced by the load imposed on the top of the pile. This paper deduced a plastic zone of rock around a single pile and obtained the shaft resistance of a rock-socketed pile based on the theories of cavity expansion and shear strength. The research results showed that the magnitude of the radial force in the socketed portion of a rock-socketed pile was related to the pile diameter, Poisson’s ratio, and properties of the surrounding rock. The influence area of rock decreased with increasing pile diameter. The radial force and lateral friction decreased with the increasing relative stiffnesses of the pile and rock. The radial stress on the elastic–plastic interface can be analytically determined based on the rock properties and depth. A field test was used to validate the proposed method, and a good agreement was obtained between the field data and predicted results of the proposed method. The research results in this paper are beneficial to guide actual practice.