Field study on the bearing capacity and deformation characteristics of rock-socketed piles with large diameter and length

Rock-socketed piles with large-diameter have gradually become the preferred foundation type for large-scale structures under complex geological conditions due to their advantages such as high bearing capacity and low settlement. Based on the Ningbo LNG project, this study focuses on analyzing and summarizing the strain distribution, Poisson's ratio variation, axial force transfer, side resistance mobilization, and compression deformation behavior of large-diameter super-long piles. Test data indicate that static load tests of heavy-tonnage pile foundations are prone to eccentric effects, with a maximum sectional eccentricity ratio reaching 1.9, and the influence range of the "Saint-Venant effect" at the pile top exceeding one pile diameter (1.5m). Affected by boundary conditions and loading levels, the Poisson's ratio of pile concrete fluctuates between 0.1-0.2, with tangential values generally lower than radial ones. Under a load of 24,000 kN, the measured maximum settlement at the pile top was 14.3 mm, with calculated pile body compression accounting for approximately 76.2% and side friction resistance contributing over 77.3%, demonstrating the "side resistance-dominated, end resistance-delayed" bearing characteristics of super-long rock-socketed piles. The research findings quantitatively reveal the nonlinear relationship between pile side friction resistance and pile-soil relative displacement, which can be applied to performance-based design of rock-socketed piles with large diameter and length.