Development of a Swelling Model for Strong Expansive Soil Under K0 Stress State for Building Foundation Applications

This study explores the swelling behavior of strong expansive soil from the Nanyang Section II canal bed of the South-to-North Water Diversion Middle Route Project, with practical relevance to foundation engineering. A total of 45 one-dimensional swelling tests were performed using a lever-type consolidation apparatus under K0 stress conditions. The test matrix covered three dry densities (1.45, 1.50, and 1.55 g/cm3), three initial moisture contents (20%, 25%, and 30%) and five overburden pressures (0, 12.5, 25, 50, and 100 kPa). Results indicated that the swelling rate decreased in a logarithmic pattern with increasing pressure and was strongly influenced by compaction level and initial moisture. The highest observed swelling rate was 14.96% under zero loading. Based on the experimental data, a semi-empirical model was developed that accounts for dry density, water content, and overburden pressure. The model showed strong agreement with the test results (R2 = 0.9888) and was further validated using an independent dataset (dry density = 1.60 g/cm3), achieving R2 = 0.981 and RMSE = 0.606%. The proposed model serves as a practical tool for predicting swelling-induced deformation and supports engineering decisions on compaction, moisture conditioning, and foundation stability in expansive soil regions.