The deformation characteristics of silty soils under vibrational loads can easily change due to the wetting process, leading to the failure of roadbed structures. Commonly used methods for improving silty soils in engineering often yield unsatisfactory economic and ecological outcomes. As an environment-friendly soil improvement material, Xanthan gum has broad application prospects and is therefore considered a solidifying agent for enhancing silty soil properties in the Yellow River Basin. In this study, a series of tests is conducted using a scanning electron microscope and a dynamic triaxial testing apparatus to investigate the microstructure and dynamic deformation characteristics of unsaturated silty soil with varying xanthan gum contents during the wetting process. The results show that xanthan gum effectively fills voids between soil particles and adheres to their surfaces, forming fibrous and network structures. This modification enhances the inherent properties of the silty soil and significantly improves its stability under dynamic loading. Specifically, with increasing xanthan gum content, the dynamic shear modulus increases while the damping ratio decreases. During the wetting process, as suction decreases, the dynamic shear modulus decreases while the damping ratio increases. Xanthan gum reduces the sensitivity of the dynamic deformation characteristics of the treated silty soil to changes in suction levels. Finally, based on the modified Hardin-Drnevich hyperbolic model, a predictive model for the dynamic shear modulus and damping ratio of treated silty soil is proposed, considering the xanthan gum content. These research findings provide a theoretical basis for the construction and maintenance of water conservancy, slope stabilization, and roadbed projects in the Yellow River Basin. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

The precipitation and intrusion of sodium chloride into pavement structures is inevitable in coastal regions, which can affect the mechanical properties of the road base courses. To investigate this problem, samples with sodium chloride solution were cured in a thermostatic chamber until they reached the specified states of sodium chloride precipitation within the pores. A critical crystallization degree (wc) was discovered by computerized tomography scan, corresponding to the start of the formation of porous salt crust cementing the soil particles. A series of unsaturated large-scale triaxial shear tests were then conducted under various states of salt crystallization. The results showed that in the early stages of crystallization (i.e., w wc, owing to the increasing adsorption and cementation effects of the salt crust, rapid growth was observed for the peak stress, internal friction angle, and apparent cohesion of the road base aggregates. Considering the influence of salt precipitation, a modified shear strength criterion that can predict the shear strength of the salinized road base aggregates was formulated.