Abstract: The deformation mechanism of composite ground with gravel piles in flexible foundation is thoroughly studied, and the effect of a cross-sectional shear stress is introduced in the analysis of radial displacement mode considering the lateral bulging and integrity of the piles. Therefore, a bulging load transfer mode of gravel piles is established. Then, a differential equation for the bulging deformation of gravel piles in flexible foundation is derived based on the load transfer law. The pile-soil stress ratio and settlement flexible foundation are obtained. Finally, the proposed method is proved to be of certain rationality and feasibility through case studies and numerical simulations, and the parameter analysis indicates that increasing pile-soil modulus ratio and reducing the replacement rate will increase the pile-soil stress ratio, while the load level will affect the radial bulging deformation degree.