A Review of Saline Soil Subgrade Deterioration in High-Altitude Cold Regions: Mechanisms， Risk Indicators， and Mitigation from a THSM Perspective

Saline soil subgrades in high-altitude cold regions are increasingly affected by salt expansion， salt dissolution， and salt corrosion under the combined influence of permafrost degradation and climate warming and humidification. This paper reviews recent advances in the mechanisms， representative empirical indicators， risk assessment approaches， and mitigation strategies of these subgrade diseases. Existing studies indicate that salt expansion mainly involves sulfate crystallization and chemically induced expansion， whereas salt dissolution is primarily associated with hygroscopic chloride salts， and salt corrosion is closely related to coupled water-salt migration and freeze-thaw action. Recent evidence also suggests that the evolution of these diseases is governed by coupled thermo-hydro-salinity-mechanical (THSM) interactions. Current mitigation measures can be broadly grouped into water-salt regulation and soil improvement. The former mainly includes isolation barriers and hydrophobic soil， which suppress capillary rise and infiltration， whereas the latter mainly includes replacement and soil amendment， which improve soil properties or reduce the adverse effects of soluble salts. Although substantial progress has been made， challenges remain in quantitative long-term deformation prediction， field validation of emerging materials， and clarification of coupled degradation mechanisms under harsh environmental conditions. Future work may therefore focus on THSM coupling， long-term durability， and cost-effective technologies for sustained subgrade service in cold saline regions.