Abstract: Expansive soils are widely distributed across southwestern and northwestern China, and variations in water content exert a pronounced influence on their engineering behavior. Nuclear magnetic resonance (NMR) technology enables nondestructive quantification of water residing in different pore domains of soil. In this study, a series of water-absorption swelling tests were conducted on expansive-soil specimens using an NMR experimental system in conjunction with a conventional consolidation apparatus to investigate the influence of initial water content on swelling behavior. Test results indicate that increasing initial water content suppresses the swelling potential of expansive soil. Moreover, at higher dry densities, the differences in void ratio after hygroscopic swelling among specimens with different initial water contents become more pronounced. Correspondingly, the NMR results show that higher initial water content leads to lower NMR signal peak amplitudes, smaller T-2 values associated with the peak, and reduced area enclosed by the curve and the x-axis. Under high vertical stress, expansive soils with lower dry density and higher water content are more prone to shrinkage.

Key words: Nuclear Magnetic Resonance Technique, Expansive Soils, Initial Water Content, Shrinkage Phenomenon