Strength and hydraulics of hydrogel-based polymer solidified sandy silt

Objective Addressing the inherent instability of sandy silt at active layer of permafrost regions in Qinghai-Tibet Plateau, this study investigated the efficacy of hydrogel-based polymers for solidification treatment. The objective was to enhance their hydraulic properties in freeze-thaw cycling conditions. Method A comprehensive characterization was conducted through a series of experiments, e.g., unconfined compressive strength, permeability coefficient, 4 weeks freeze-thaw cycling with all-around water saturation, scanning electron microscopy, X-ray diffraction, and mercury intrusion porosimetry. These investigations aimed to delineate the influence of hydrogel-based polymer content on mechanical properties and hydrological behavior of sandy silty, concurrently exploring the underlying solidification mechanisms. Result The hydrogel-based polymer significantly enhanced the resistance to disintegration, permeability, and freeze-thaw cyclic performance of sandy silty, demonstrating a favorable solidification effect. Notably, with polymer content of 10%, the 28-day unconfined compressive strength exhibited an increment of 80% relative to the plain soil; while the permeability coefficient was concomitantly reduced by two orders of magnitude. Furthermore, after ten freeze-thaw cycles in saturated conditions, the mass loss of the treated specimens registered a mere 8%, underscoring exceptional freeze-thaw stability. However, it was noted that the polymer content should not exceed 15%, as this could adversely affect the unconfined compressive strength in 7 days. The hydrogel formed a dense interstitial infilling among soil particles and simultaneously adhered to their surfaces. This contributed to a substantial reduction in the proportion of macropores (>1 000 nm), a decrease in the average pore diameter, and an increase in tortuosity. Consequently, these structural modifications effectively extended seepage pathways and refined pore channels, thereby synergistically promoting both the strength and hydrologic stability of soil mass. Conclusion The hydrogel-based polymer has good application potential in the solidification and permeability control of permafrost. The findings provide feasible technical paths and theoretical basis for relevant engineering practice.