In response to the vulnerable problem of high-piled wharf pile foundations in marine environments,although steel sleeve grouting technology has the potential for reinforcement,the bending design lacks theoretical support.Through experiments and theoretical modeling,the research aims to reveal its mechanical properties and failure mechanisms,propose quantitative calculation methods,and support the improvement of engineering safety.The experiment used four different parameters of steel sleeve grouting reinforcement PHC pipe pile specimens,with key variables including grouting material thickness (40,50,60 mm) and steel sleeve thickness (5,8 mm).Through graded loading and monitoring of the load-strain response,the results indicate that increasing the thickness of both the grouting material and the steel sleeve can improve the flexural performance,and the strengthening effect of the steel sleeve thickness is more significant.Furthermore,the calculation formula for flexural bearing capacity is derived based on the plane section assumption.Experimental verification shows that the error is only 2.16%-6.58%,indicating satisfactory reliability.The research results provide a theoretical basis and quantitative calculation method for the application of steel sleeve grouting technology in the flexural design of pile foundations,which has important reference value for improving the safety and accuracy of the repair and reinforcement of high-piled wharves and similar engineering structures.