The contact relationship at the pile-soil interface is a key issue that should be considered in numerical calculations of the stress and deformation of hydraulic structures since the significant differences in the mechanical properties between the pile foundations and the foundation soil.To address the pile-soil interface contact problem,a large-scale multifunctional pile-soil interface shear apparatus independently developed is used to conduct experimental study on the frictional characteristics of the contact interface under different normal force and pile material conditions.The experimental results indicate that the interface shear stress increases with the growth of shear displacement until it reaches a peak value and then stabilizes.This peak value is proportional to the normal stress and is related to the roughness of the pile material.Based on contact mechanics,a calculation model for the pile-soil interface friction coefficient is established,considering both the undamaged and damaged states of the interface soil.The error between the calculated values of the model and the experimental data from interface friction tests is less than 5%,accurately reflecting the frictional characteristics of the pile-soil interface.This model is applied to analyze the bearing characteristics and structural stress-deformation of PHC piles in a lock chamber.The single pile load-displacement relationship and the overall structural displacement calculation results are consistent with field load test results and monitoring data.This model will contribute to enhancing the accuracy offorce and deformation analysis for hydraulic structures.