Study on the Direct Shear Mechanical Behavior and Discrete Element Numerical Simulation of Saline Soil Stabilized with Ionic Additives and Inorganic Materials

[Objective] Saline soils exhibit special engineering characteristics such as collapsibility, salt swelling, and corrosiveness, which bring serious harm to the project construction. Therefore, identifying an economical and effective stabilization method to enhance their engineering applicability holds significant scientific and practical importance. [Methods] In this study, a series of laboratory direct shear tests were conducted on saline soil specimens stabilized with a combination of an ionic additive, lime, and fly ash to investigate its macroscopic mechanical properties. Furthermore, a discrete element model of the stabilized saline soil was developed to explore the particle displacement and force chain evolution during shearing from a mesoscopic perspective. [Results] The strength evolution of the stabilized soil was investigated, revealing that the addition of the ionic additive significantly improves the mechanical properties of lime–fly ash stabilized saline soil. The stabilized saline soil specimens showed obvious brittle failure characteristics. The shear strength of the ISS-stabilized soil peaked at an ISS concentration of 6%, beyond which further addition of ISS led to a strength reduction. [Conclusion] ISS effectively enhances the strength of inorganic material-stabilized saline soil, with its influence being related to variations in soil particle surface water film thickness and coverage extent of reaction products. Simulation results reveal that the damage curve progresses through three stages: i.e. stable development, exponential growth, and stabilization. Then a microscopic damage factor expression was proposed, and the damage evolution behavior under loading was subsequently revealed.