<p>The post-grouting process can significantly improve the ultimate bearing capacity of individual piles. Still, there is currently a lack of mechanistic analysis of the bearing capacity of individual piles under the action of post-grouting. This paper makes the following two innovations. (1) Based on reasonable basic assumptions, the pile is regarded as an ideal elastic body, and the soil around the pile is regarded as an ideal elastoplastic body. The failure mode of the soil at the pile tip under vertical static loading of the pile is proposed, and the analytical expression for the ultimate bearing capacity of the soil under vertical static loading of the pile is derived. (2) The grouting reinforcement body around the pile is regarded as a solid material with geometric self-similarity, and the elastoplastic assumption of the surrounding soil also utilizes the compressive action between the reinforced area and the surrounding soil. The bearing capacity analytical expression based on the grouting reinforcement body is derived using the virtual displacement principle. By combining the bearing capacity realization mode of the single pile and the post-grouted reinforced soil, the method for calculating the bearing capacity of the grouted soil is determined, providing a new idea and solution for solving practical engineering problems. By comparing the measured ultimate bearing capacity of a postgrouted single pile, the results show that the proposed calculation model can be used for preliminary estimation of the bearing capacity of post-grouted single piles.</p>