Abstract: The thick soft soils underlying the Wuhan Motor-racing Circuit have caused substantial challenges to the engineering design and construction. Coping with these issues requires the determination of the negative skin friction force and the neutral point position. To verify the appropriateness of the PHC pile in this site and provide technical guidance for possible future piled foundation enhancement design, long-term monitoring of the settlement of the pile and the surrounding soil was performed. The time dependence of the neutral point was studied according to the settlement of the pile and surrounding soil. The results indicate that the settlement of the PHC pile is 1/6 of that of the surrounding soil, which confirms significant negative skin friction. The layered settlement observation shows that the settlement of the foundation soil is mainly caused by the compression of the soft soils within 13 m depth. In the studied sites, the neutral point position is elevated with time on the pile and tends to correspond to a shallower position of the neutral point. In addition, the variation of neutral point position with time consists of three stages and can be described using an exponential model. Such a model predicts better than the construction codes do, and the predicted stable values for the neutral point position in the two test sites are 4.55 m and 5.72 m, respectively. The current results also confirm the effectiveness of geogrids in reducing the settlement of surrounding soil as well as the differential settlement. Besides, geogrids lead to an elevated neutral point position and reduced negative skin friction. This paper is helpful in understanding how negative skin friction affects the performance of the piled foundation.