Horizontal Infiltration Characteristics of Aeolian Sand under Different Dry Densities and Water Head Conditions

Horizontal water migration critically governs moisture distribution and hidden hazards in aeolian sand subgrades, particularly where roadbeds are exposed to lateral recharge from adjacent rivers. This study investigates the horizontal infiltration behavior of aeolian sand through a custom-designed dynamic monitoring platform, considering three dry densities (1.5, 1.6, and 1.7 g/cm3) and four water heads (10, 15, 20, and 25 cm). The evolution of the wetting front, moisture content distribution, infiltration rate, and cumulative infiltration was systematically analyzed. Results show that dry density and water head significantly influence moisture migration, with their effects attenuating with depth. Increasing dry density from 1.5 to 1.7 g/cm3 reduces the stable water content by 6.48% in the surface layer but only by 3.81% in the deeper layer, whereas raising the water head from 10 to 25 cm increases it by 20.60% and 5.78%, respectively, highlighting the dominant role of the hydraulic head in surface moisture gain. The wetting front exhibits a convex shape, with transport rates increasing along the vertical profile, indicating enhanced hydraulic connectivity at depth. The Horton and Kostiakov models accurately capture the temporal variations in infiltration rate and cumulative infiltration, with achieving coefficients of determination (R2) of 0.997 and 0.991, respectively. Notably, limiting the ponding head is found to be more effective than merely increasing compaction for controlling lateral migration. These findings provide quantitative insights and theoretical guidance for moisture control and stability assessment in aeolian sand subgrade engineering adjacent to dynamic water systems.