Deformation Characteristics and Prediction Model of Xanthan Gum-Treated Weakly Expansive Soil

Natural drying-wetting cycles can easily change the deformation characteristics of expansive soil, leading to uneven settlement and collapse phenomena in the long-term operation period of related projects. To pursue further green and sustainable geotechnical development, environmentally friendly Xanthan gum (XG) was adopted to improve the soil engineering properties, but studies on the deformation behavior of XG-treated expansive soils are limited. A series of water immersion expansion deformation tests is conducted on expansive soil with different XG ratios and initial dry densities under different vertical pressures. At the same time, combined with the scanning electron microscope test, the mechanism of the deformation of XG-treated expansive soil was revealed. The results show that XG effectively fills the voids between soil particles, forming fibrous and reticular structures, and that XG absorbs water to form a gel-like matrix (Gel). For XG ratio ≤ 0.5%, the swelling deformation of the XG-treated expansive soil is restrained, and the constraining effect of soil particles on the Gels is dominant. For XG ratio > 0.5%, the swelling effect of the Gel formed by hydration is dominant, and the constraining effect of soil particles on the Gels is not obvious. Correspondingly, the final void ratio of the XG-treated expansive soil at saturation first decreases and then increases with increasing XG ratio. Finally, a predictive model for the saturated final void ratio of XG-treated weakly expansive soil is proposed. The above research results can serve the national strategy of promoting the high-quality development of the subsequent South-to-North Water Diversion Project.