The study looked at how compacted expansive soil in Nanyang swells under different conditions. They found that the swelling ratio increases with vertical loads in a specific way. By using certain formulas, engineers can predict and control the soil's swelling in real projects. Adding a layer of non-expansive soil on top of the medium expansive soil slope can help reduce deformation. This research provides valuable guidance for designing and building slopes with expansive soil in the South-to-North Water Diversion Project.